In 3.5e magic item creation rules for skill competence is [Bonus Squared × 100gp].

So, one could create the following pricing scheme:

Standard Map (+0 Survival): 25g

Good Map (+1 Bonus): 100g

Great Map (+2 Bonus): 400g

Etc...

Or you could have the bonuses be:

Standard (Flavor item): Contains obvious information

Good: Contains information the players don't already know.

Great: Grants advantage on navigation checks

Magic: Grants advantage on navigation checks and can reveal new information as the players explore.

The bonus only applies to navigation on the scale of the map, so a world map would provide no bonus for city navigation.