Prism said:The PHB sets the price of a complete spell book at 5000gp (P179)
Space in the Spellbook: A spell takes up one page of the spellbook per spell level. Even a 0-level spell (cantrip) takes one page. A spellbook has one hundred pages.
Materials and Costs: Materials for writing the spell cost 100 gp per page.
Selling a Spellbook
Captured spellbooks can be sold for a gp amount equal to one-half the cost of purchasing and inscribing the spells within (that is, one-half of 100 gp per page of spells). A spellbook entirely filled with spells (that is, with one hundred pages of spells inscribed in it) is worth 5,000 gp.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.