Steppers vs Steppers

I am sourcing parts for a large machine and because of a tight budget we need to go for large steppers instead of our usual servo's.
I have no experience in steppers. When looking at different sources like web shops, eBay, catalogs etc there is a pretty big difference in pricing.

In general terms, are there much differences in different steppers?
I mean, steppers are steppers. Or?..