You're great idea is just that, you're great idea, something in your mind that has not been developed, tested or marketed, so its value should represent this, and therefore affordable to interested companies who are prepared to take a chance and develop it further.

Its future value can only be determined by the interested companies who have received it and understand the ongoing costs. But becouse these companies can see its potential they will pay a certain ammount to secure its rights.

Its present value is really what you think its worth in relation to the effort you have put into it & what you do with it in the future, if anything at all?