Whatever both parties accept is OK, there is no book value. As to us, we compare the suggested valuation primarily against what has been achieved to date, secondarily to what the plan is “promising”. The higher the price tag, the more you are expected to have already, and the more is expected from you going forward. And while there is no “List” price, professional investors know what kind of companies have been able to close rounds at what valuations, which gives a comparable. Worth noting is that any founder with experience in fundraising will tell you that more important than the valuation, or even the amount raised, is that the process is quick and smooth, allowing you to get back to doing business as soon as possible. If you try something that is unrealistic, you will learn the hard way the wisdom behind that.