The Bat Jar Conjecture - S1-E13
Trivia: When Leonard, Howard and Raj are contemplating who to have as the fourth member of their Physics Bowl team, Raj says, "You know who's apparently very smart is the girl who played TV's 'Blossom'. She got a Ph.d in Neuroscience or something." The girl he's referring to is actress Mayim Bialik, who plays Amy Farrah Fowler in later episodes of The Big Bang Theory. Interestingly, she is the only recurring cast member on the show that actually does have a Ph.d in real life.
Suggested correction: Not being able to afford doesn't necessarily mean he doesn't have the money, especially a man like Sheldon. He works with a budget and he sticks to it. In his budget he has a certain amount set aside for rent, anything more than that and he can't afford it alone.
Nonsense. If he was sticking to a "rigid budget" he wouldn't have even thought of lending a hopeless credit risk like Penny a single cent. Instead he throws a huge bankroll at her without even discussing a repayment plan.
Rubbish, I stick to a strict budget but still have the money to lend to close friends. Like Penny is to him.
He might have different budgets for different things. People could get a higher margin because they could be of more use to the scientific mind of Sheldon.