The biggest issue is you have information asymmetry between the domain expert and the developer. Because developers can't tell the difference between great idea

The biggest issue is you have information asymmetry between the domain expert and the developer. Because developers can't tell the difference between great ideas and bad ones they'll pay the same price on the market. If all ideas sell for the same amount and you're a domain expert than it makes sense to keep your best ideas and sell your worst ones. This drives down the average quality of an idea as well as price which means less domain experts are willing to sell at market price which drives down quality, etc... Very similarly to an insurance death spiral. A similar process also drives down the average quality of the developer working on the work.