Geometer is a prestige class in Complete Arcane that gains a special class feature at level 2:

a geometer uses a unique system for recording the details of a spell that drastically reduces the expense of maintaining spellbooks. Every spell he learns from now on requires only a single page in his spellbook. It still takes 24 hours to scribe a spell into a spellbook and materials costing 100 gp per page

This means that a Geometer only needs one page per spell, regardles of spell level when writing a spell in a spellbook. Without this feature you normally need to write one page per spell level.

Eidetic Spellcaster is an Alternative Class Feature for Wizards that replaces the Scribe Scroll Feat (can be seen here):

You do not need a spellbook, either to record spells you know or to prepare known spells. You can learn spells normally, either through gaining levels in wizard or learning from other spellbooks, and you must pay all the normal costs for learning new spells (used instead in special incenses rather than inks), but you do not need to put them into a spellbook

This means that you remember spellbook pages and do not neet to write them. However the cost remains the same, you just do not need a spellbook.

Question: Since you can commit spellbook pages to memory instead of writing them to a spellbook, and you only need one page to store any spell, does this mean that you can save money in special incenses when adding a spell to your repertoire? i.e. special incenses only need to cost as much as writing one spellbook page instead of one per spell level

Geometer is a prestige class in Complete Arcane that gains a special class feature at level 2:

A geometer uses a unique system for recording the details of a spell that drastically reduces the expense of maintaining spellbooks. Every spell he learns from now on requires only a single page in his spellbook. It still takes 24 hours to scribe a spell into a spellbook and materials costing 100 gp per page

This means that a Geometer only needs one page per spell, regardles of spell level when writing a spell in a spellbook. Without this feature you normally need to write one page per spell level.

Eidetic Spellcaster is an Alternative Class Feature for Wizards that replaces the Scribe Scroll Feat (can be seen here):

You do not need a spellbook, either to record spells you know or to prepare known spells. You can learn spells normally, either through gaining levels in wizard or learning from other spellbooks, and you must pay all the normal costs for learning new spells (used instead in special incenses rather than inks), but you do not need to put them into a spellbook

This means that you remember spellbook pages and do not neet to write them. However the cost remains the same, you just do not need a spellbook.

Question: Since you can commit spellbook pages to memory instead of writing them to a spellbook, and you only need one page to store any spell, does this mean that you can save money in special incenses when adding a spell to your repertoire? i.e. special incenses only need to cost as much as writing one spellbook page instead of one per spell level