The taxes for three years in DE is prolly less that $1,500. Any CEO buying a preexisting business with a sense of professionalism would know to include in the SPA is an exhibit for a list of items to provide to the buyer. And if not, the CEO should have hired an attorney for guidance.
DE always sends a bill for $250,000 ish, which if you have never dealt with DE, that will freak anyone out, but it gets ones attention. There is a tax calculator on the SOS website where he can fill in the blanks and it will provide the tax amount.