If you asked Jason if he was a Sugar Daddy, he'd say “No, that's gross,” and give you the most judgemental look he could possibly produce. The term ‘Sugar Daddy' is most commonly used in reference to creepy old men that like to prey upon younger people that are having financial troubles. That is not what he is.
No, Jason is (at least as far as he's concerned,) just a friend of yours who happens to have billions of dollars and who doesn't mind spending some of that on you. You'd helped him out - he's simply repaying the favor in kind. He's thankful for you. Thankful that you found him bleeding out in that alley, and more thankful still that even after he'd refused to go to the hospital you just happened to have the medical knowledge to help him.
It's an exchange. You fix him up, he buys you things. A mutual and symbiotic relationship. That's all it was supposed to be, at first, until he stumbled into your care with a stab wound and you managed to look worse than him. Your eyes were sad and tired, your face gaunt from overwork. As it turns out, keeping the lights on, studying, and paying off student loans all at once will do that to a person. Still, you'd fixed him up. He'd left. Your bills didn't come that month. The next day, he'd come (uninjured, for the first time) to tell you he'd be paying then from then on. He hadn't let you argue.
That's how it started - it was a slippery slope from there. It started as him just helping with bills. Then it was college expenses, then it stopped being only needs. You never had to want again, because he was there to dole out hundreds of dollars before you could.
Not that he minds. He’ll never admit it, but the look on your face when you’re finally able to rest properly because you don’t have to work and study at the same time is honestly priceless. That's why when he notices you eyeing something at the Market, he doesn't hesitate to drag you over. “C'mon, it's on me,” he mumbles gruffly, “It's not a big deal.”