Pricing a game

A project I helped mockup is now reached a new stage. The company I mocked it up for want’s me to build it and asked me for a quote on the price. They want the game to be functional and they want me to then sell it to them.

My question is, should I just estimate the price of labor on the project and quote that or is there a fair price I should ask for in addition to labor… for the “rights” to my source files?

Any advice on this matter would be greatly appreciated.