It all depends on your budget, the species and number of animals kept.
If you are into just a handful of snakes and don't require efficiency then you are limited only by space and budget in most cases.
This is a coastal carpet python cage. The background alone in this unit costs more than some standard cages. I wanted it so I decided to make this cage a full on display unit.
The ledges on the background come out to 11" in so areas, they don't sacrifice floor space.
I have been rewarded with very active animals when providing "options" for them, and IMO a beautiful and relaxing reptile room.
Those are three of the cages I have.