I agree about the importance of managing the deal yourself. That said, there's definitely a way to get a sense for what the counterparty will pay without asking

I agree about the importance of managing the deal yourself. That said, there's definitely a way to get a sense for what the counterparty will pay without asking for an upfront price. He needs to know how the acquiring company is thinking about the acquisition. Are they buying the technology? Purchasing a revenue stream? Buying a marketing channel? A combination of the above? If this is primarily a technology acquisition the price can be discussed independent of sensitive business data. If it is a revenue play you can talk about multiples. And if it is a marketing play you can talk about they value users. The idea is to build consensus around an informal model for how to value the business without going into detail. It requires sharing some data, but not necessarily opening the books. I also think its reasonable to have a non-refundable deposit in exchange for going through the due diligence procedure. I wouldn't consider ballpark figures sensitive for my own business, but wouldn't agree to go through due diligence without being sure it wasn't a fishing expedition.