But if anything this an argument in favour of the idea that ideas do have value, as it's equivalent to the situation where the capitalist pays $10,000 to set up

But if anything this an argument in favour of the idea that ideas do have value, as it's equivalent to the situation where the capitalist pays $10,000 to set up the ice cream stand and wanders off while their partner does all the work. The arrangement may be unfair on some level but that's a whole different question.