No core mechanics in 5th edition in regards to page usage.
As mentioned above, the section of the PHB with your spellbook's information/appearance allows you to use anything that you could record information on, at the cost of 2hrs and 50gp (per level of spell) for new spells, and half as much for ones you already have prepared/recorded.
In the AL module 'The Visitor,' the antagonist's spellbook was a collection of brass plates/sheets, attached together by a large brass ring.
Your entire spellbook could be a gilt tome, a loose collection of notes, a leather volume, etc. The point is that you can make it as simple, flourished/flavorful as you like, as per the core mechanics.
If the DM wishes to put any additional costs to learning spell/skills, that's between them and their players to figure out. As far as Adventure's League goes, it is my understanding that you must use the information that is openly available as per the PHB/ errata for that edition. If it's not mentioned, then it has been excluded from that edition, (similar to what happened with paladins and monks between the different editions)