If the people working for the company has finished making the product, then after that they would have to be tasked with making a new product. So, yes, if the product is delivered then there shouldn't be any dip in revenue if you fire the people who made it.

Companies keep these productive people if they want to grow and deliver even more products. They fire these productive people if they're not aiming for more growth at the moment.

I use some old software that nobody has been working on for a decade and it still works perfectly, to give an example.