I am a DM and I altered the rules for scribing spells into spellbooks. I don't like the rules as written simply because they have a lot of logical holes in them (from my point of view). My rules don't completely fix all these holes, but I patch them up well enough to satisfy myself.
Scribing costs 1/10th of normal (10GP per page).
The scribing costs are the cost for the ink used. This ink is a comodity that can be purchased or found in my game world. Therefore you buy X amount of ink before you leave town. If you scribe X amount of spells and run out of ink, no more scribing until you somehow obtain more ink. This ink is the same ink used for scribing spells onto scrolls. (Note - I have created comodities for all the item creation feats in my game in the form of potion ingredients, magical oils to be applied during the crafting of weapons & armor, etc. These things can be found as treasure.)
The special ink used is created through alchemical processes. Therefore, if you want to buy the raw materials and spend the time creating the ink, you can cut the cost in half again. If you want to forage about for the raw materials and brew up a batch of ink yourself, you can cut the cost to zero in terms of GP. But be prepared to spend a LOT of time looking for the rare herbs involved.
Scribing time is the same as in the PHB.
You don't get free spells when you go up levels.
So there they are. I have presented them on these boards before and was told that these rules were way to lenient for the wizard. That my be, but it hasn't been proven yet since none of the players has wanted to play a wizard so far. That alone makes me think these rules aren't too broken.
As someone mentioned above, the DM controls how much time and money are available to the party. My group has tended to have not very much of either most of the time. But these rules do put me in complete control of what Wizard spells are available in my game. Which is not to say that I wouldn't listen to a player's preferences for spells. But I no longer have to worry about every encounter likely starting with a fireball as soon as the party reaches 5th level.