The Flers were overjoyed about Jason's offer, and only Greg seemed to hesitate because he didn't want to exploit his best friend.
Yet, Jason didn't hesitate, as he tried to find a way to make his friend feel less awkward.
"If you feel uncomfortable, you can just pay me back later...You can take it as a loan, but it doesn't really matter!"
In the end, he felt extremely thankful to the Flers because they had brought him to Cyro-City, which was one of the most important and life-changing decisions he could have ever taken.
If not for them, he might still have been with the unevolved Artemis in Artes-city, where he grew up.
As such, he felt more comfortable in expressing his gratitude to the family. He had found a perfect way in doing so by giving them enough funds to purchase the required ingredients to concoct the evolution solution for the reinforced horned bull, Taurus.