I've been searching with Google and Bing all morning and haven't found anything. I can't afford a $3000 cad system. I just want an affordable, hobby-level, parametric modeler.
I can warmly recommend Luxology Modo. It's still a bit on the pricey side ($995), but that's a great deal less than $3000. I think this is the best "in-between" big-bucks and low budget solutions, where you get the most "bang for the buck."
They also offer a free 15 day trial, or a $25 day production evaluation license, where you also get full access to their translators, SDKs, asset sharing sites etc. I encourage you to give it a whirl!
On second thought; this might not be what you're looking for. I missed the word "parametric" in your title - my apologies. I think you'll still be able to use Modo for some "hard-surface-modelling," but it might not be able to offer you that "architectural precision."
I use Alibre Hobby version it is 99 dollars, and has a lot of the features of the Pro version. Since it allows the export you can send what you deign out to rapid prototyping houses. It is a lot of fun. Also the parametric stuff that they do is a real life saver if you are designing parts for projects. Check out the videos.
Since this has the OSX tag, then you will need to load windows either in a VM or Bootcamp.