[martinced]

"There's a lot more than opportunity cost. There's the actual money in my pocket lost from the (probably very good) salary that I would be making at an established company."

I'm probably mistaken on this but isn't your second sentence precisely the very definition of "opportunity cost"?

I mean, the opportunity cost isn't what it's going to cost you to buy ramen and rent EC2 instances: the opportunity cost is the money you're not winning should you be working for a company actually paying you.