I agree that the prices are waaaaay to high. There are two ways of looking at it (IMHO):
1. The spellbook has no power, it is just a set of instructions. In this case the cost for scribing should be no more than for basic items of that quality.
2. The spellbook can also be used as a scroll, with the wizard casting out of it (this will, of course, erase the spell). In this case the spellbook acts as a sort of magically charged template through which the wizard accesses his spells. This method may warrant something close to that of a scrolls price which....
I sometimes do scrolls as requiring special ink/paper to scribe. To scribe a special scroll, one needs to buy the correct ingredients for that ink. Alternatively, they can collect the components they need themselves during their adventures. For example, a flesh to stone spell (or whatever it's called) might require:
1 oz Giant Squid ink
An eye from a basilisk
A piece of skin from a medusa
etc.
This is just off the top of my head, but you get the general idea. Ideally, the price for these components should add up to about the cost of that scroll. This just adds an extra option for the players. A similar method would be used with a spell book using option 2.