There are many 'stand-alone' music systems that are more affordable than what Crestron offers, but I don't think many are below $5K for 10 zones.
Your Crestron salesman should be familiar with some of the more budget-friendly options.
Each of these systems - few from Nuvo, couple from Russound, Niles, many others - can accomodate 6-8 zones. For another few thousand dollars, you can purchase an expansion amp to bring you to 10. And the music server would cost another few thousand. Look for systems with 232 and/or IP control - your Crestron dealer may be able to get a list of systems that would integrate well with the system.
Don't forget the music server source component, I think I've seen Squeezebox mentioned often with Crestron systems.
There are lots of options with Crestron. Again, the dealer would be the best resource.
I've been pleased with a Nuvo Grand Concerto system, with the amp expander, and MPS4 music server. It can do 6 zones without the expander, 8 zones with 2 small additional amps, 12 zones with the multichannel amp expander, and 16 zones total.
The Russound C-Series, I think, can do 8 zones without an expansion multichannel amp.
I really like a keypad in each zone - these stand-alone systems often ship with keypads (Nuvo for one). My Nuvo keypads provide metadata (artist, song, album info), as well as control.
Programming costs money, but the more popular stand-alone systems are not super expensive to program for Crestron.