Both are secret organizations established to protect world peace, but compared to S.H.I.E.L.D., Kamar-Taj has a much longer history and tradition, and its way of doing things is also much more reliable.
After all, the members of the organization are all sorcerers. After more or less mastering some extraordinary abilities, the personal strength of the sorcerers has exceeded the scope that national agencies can manage. Coupled with the fact that Kamar-Taj has never been exposed to the world, sorcerers are not subject to restrictions and management from official agencies, whether in daily life or combat operations.
Being detached from the world is one of Kamar-Taj's greatest characteristics.
However, everything has two sides.
Not dealing with government agencies and living a reclusive life certainly allows for freedom from restrictions. But on the other hand, it is precisely because of adhering to this tradition and deliberately reducing contact with the world that Kamar-Taj's economic sources have been limited... Not to mention comparing it with S.H.I.E.L.D., which receives countless appropriations every year and occasionally launches new projects to request additional financial support; it might even be inferior to ancient temples located in famous scenic spots.
Look at the original plot of "Avengers 3." Doctor Strange and Wong were so poor that they only had one dollar and fifty cents between them, not even enough to buy a hamburger. Part of this was certainly due to Strange overcorrecting (after taking over as Sorcerer Supreme, to avoid following in the Ancient One's footsteps and attracting the covetousness of extra-dimensional demons, bringing new threats to Earth, he sealed all of Kamar-Taj's 'treasures'). But overall, the real key was Kamar-Taj's weak economic foundation.
And now... perhaps because she has been in power for too long and has long mastered the proper measure, or perhaps because her personality is inherently more lively, the Ancient One occasionally relaxes her self-restraint, acts expediently, and makes some extra money for Kamar-Taj.
In terms of economic status, it is indeed much better than after Strange took over.
But obviously, Kamar-Taj under the Ancient One's leadership is still not rich enough to be on par with S.H.I.E.L.D. and Stark. Buying a large number of potions from Shi Xiaolei at a price of ten thousand US dollars per bottle? Even if the Ancient One emptied her private piggy bank, she still couldn't afford it.
Moreover, what the Ancient One truly favored was not the red, black, and white potions that Shi Xiaolei had previously brought out, but the vitality potion displayed at that party.
Sorcerers, after all, care more about the length of their mana bar.
The Ancient One wasn't very concerned about the healing effect of the vitality potion, but she couldn't underestimate its mana-restoring function. After all, this is Marvel, where the settings are completely different from other magic worlds—sorcerers do not have a source of magic within themselves and must borrow the power of the Vishanti to successfully cast various spells.
Even if the Vishanti are easy to talk to, set very low interest rates, and occasionally offer interest-free activities, ultimately, borrowed money must still be repaid.
The Ancient One herself doesn't need to worry, as she has already signed a contract with the even more powerful Eternity and will go directly to serve the great god after death. With the Vishanti's power, they wouldn't dare disrespect Eternity and pursue the Ancient One, who is protected by him, for past debts.
But what about other sorcerers who are not protected by the great god Eternity?
Perhaps it's their souls, or some other price, but the debts that need to be repaid certainly cannot be avoided.
Just as a teacher cares for their students, the Ancient One also cares deeply about her disciples and grand-disciples. It is for this reason that she sought out Shi Xiaolei to discuss cooperation—the vitality potion, which has a mana-restoring effect, can be used as a source of magic. Although it cannot completely replace the Vishanti, with its support, sorcerers can owe a little less debt. When it comes time to repay, the pressure won't be as great.
As for why only the vitality potion was mentioned and not the mana potion specifically for restoring mana... Due to the influence of the 'System,' the Ancient One could not use the power of the Time Stone to see Shi Xiaolei's future.
At most, she could only push the timeline to 'now.' In simple terms, it was somewhat similar to watching a live broadcast; she could 'remotely' see what Shi Xiaolei did and what treasures he brought out, but she could not know what Shi Xiaolei would do next or what else he had hidden away.
Shi Xiaolei had never brought out mana potions, so the Ancient One naturally didn't know of their existence.
"Here, try this."
"Hmm? This is..." Looking at the bottle of faint blue potion in Shi Xiaolei's hand, the Ancient One was slightly surprised.
"A potion specifically for restoring mana," Shi Xiaolei said with a smile. "It's true that it can't heal injuries, which is a drawback. But in terms of mana restoration, it's not inferior to the purple potion. Considering its price is only about one-tenth of the purple potion, I personally think it should better meet your requirements."
Blinking, the Ancient One opened the stopper and took a small sip of the liquid from the small bottle.
Carefully sensing the fluctuations of magic and confirming the potion's effect. A moment later, the Ancient One opened her eyes and smiled contentedly: "Indeed, it's more suitable for sorcerers."
"I'm glad you're satisfied."
"Yes, I am very satisfied." The Ancient One nodded: "So, let's talk about how to trade."
Cash on delivery, or exchanging money for goods, was clearly not feasible. After all, Kamar-Taj was not S.H.I.E.L.D., and if Shi Xiaolei only accepted monetary transactions, they simply couldn't afford it.
Therefore, after negotiations with the Ancient One, both parties formulated a slightly special agreement.
Shi Xiaolei would supply Kamar-Taj with 1200 bottles of blue potions and 120 bottles of purple potions annually. In return, Kamar-Taj would open its doors wide for Shi Xiaolei... If his companions summoned in the future, or some friends he met in life, had talent and wished to learn magic, Kamar-Taj would accept them as agreed and dutifully guide them.
Conversely, if Shi Xiaolei's side had no need for 'commissioned study' (referring to sending people to study), then every three years, he would get an opportunity to enter Kamar-Taj's treasury and choose a magical item he or his companions desired.
"Of course, the prerequisite for choosing is that you can fully control that magical item." The Ancient One winked and said with a smile, "As you know, some of the magical items collected by Kamar-Taj are very dangerous, such as the Book of Cagliostro."
"No problem." Shi Xiaolei agreed without hesitation: "I'm not Kaecilius..."
Halfway through his sentence, Shi Xiaolei realized he had been tricked into speaking.
"Indeed, it's as I suspected." The Ancient One laughed.
"Uh, uh..."
"Relax, I didn't say I was going to do anything to you. Moreover, the future is not set in stone." As she spoke, the Ancient One raised the small blue bottle in her hand and shook it: "See, here's a variable that will affect the future's direction, isn't it?"
"Huh? You mean..."
"I didn't say anything."