I'm not sure if stimulants are adequately described as turning money into time. They generally speed up time perception, meaning that you experience the same period of time as subjectively shorter. Sure, you get more stuff done in it, but still... The formulation is perhaps misleading.
People on modafinil manage to get by with less sleep. Whether or not it's long-term healthy to cut down your total sleep with it is however another question towards which I don't know the answer.
On ChrisHallquist's post extolling the virtues of money, the top comment is Eliezer pointing out the lack of concrete examples. Can anyone think of any? This is not just hypothetical: if I think your suggestion is good, I will try it (and report back on how it went)
I care about health, improving personal skills (particularly: programming, writing, people skills), gaining respect (particularly at work), and entertainment (these days: primarily books and computer games). If you think I should care about something else, feel free to suggest it.
I am early-twenties programmer living in San Francisco. In the interest of getting advice useful to more than one person, I'll omit further personal details.
Budget: $50/day
If your idea requires significant ongoing time commitment, that is a major negative.