Solidworks has had a svn-like system built into it for the last few years: http://www.solidworks.com/sw/products/product-data-managemen...
In other words, it may be $4000, but it does what would take four or five $1000 (plus training) pieces of software to do.
The only modeller I like more for certain operations is OpenSCAD, but that's because I can understand the math operations in printed pieces in complex curves.
The one program I want to see die a firey death in source-code hell is ProEngineer, now called Creo(sote). It is patently user-unfriendly, and requires so much PITA setup to even do things like regular polygons. "Oh, you want to fillet? You better do it in the right order, or the last fillet _WILL_ fail!"
There is two different solidworks PDM products, workgroup and enterprise. We went with workgroup which is cheaper and probably better for smaller teams. Workgroup is about £1000 + £200pa per seat and no cost for the server. Enterprise from memory was about 50% more per seat and you have to a few grand for the server, plus pay someone to 'configure' it for you.
PDM workgroup is actually pretty similar to SVN, you check files out, work on them and check them back in again. Except it understands relationships between files and their meta data so you can check out an assembly in its 'as built' state and it will checkout the correct old version of the parts.
Enterprise goes much further and creates work flows for you company. Documents go through different stage gates with different people being able to make changes and approve them. It is very much design for large teams with rigourous QA. It also appears as a network drive with some nice shell extensions on Windows.
Suprisingly neither of them have a Diff built in, although solidworks does itself have that sort of tool.
As a market it is definitely ripe for disrupting, although to succeed there would need to be tight integration with the software packages (solidworks, creo, inventor etc)
I anyone on here is looking to do something in this area I would love to hear from you.
But as we all know it's been a ripe area for disruption since the 1970's. :)
At the moment it's less to do with software as it is to do with the way we share the resultant information, of which there are emerging international standards. MCAD is not my speciality but I don't think I've seen a standard for handling parametrics. Unfortunately closed standards are hard enough to get governments and industry to adopt let along open ones.
If you want a solid object modeller with parametrics that's open source and you can compile yourself, check out BRL-CAD.