A very interesting problem.
From a financial point of view, your business might be worth nothing or it might be worth millions!
From a personal satisfaction point of view, you would probably gain a lot from implementing your idea in the real World. You may have a big emotional investment in this project. But you might also be very disappointed if it does not succeed. It might succeed better under the ownership of the other people.
If you sell it today, what are your career options? Can you set up a similar project tomorrow. You may be in a better postion to do so, now that you are richer. Maybe the acquiring company needs your continued input into the project?
Can you retain a stake in the project, so that you will benefit if it does become very successful commercially?
If one company is interested, maybe there are other possible buyers and you could get an auction going.
Have you a financial plan? An estimate of market size? What profit would the company make? As a rough guide, ten times the potential profits would be starting price.
Post some more details if possible.
Brendan