The instruments have appreciated. Virtually all my instruments and some of my amps are so called "vintage" or boutique. I'd guess that on average, my instruments and amps are worth 50% more now than when I purchased them.
My recording gear is about a wash. I've bought almost all my recording stuff used (except my Lynx Aurora which I bought on sale), most of it is analog, and some of it actually has appreciated a bit (mics). So overall, I could probably get what I have in it, or darn close to it, if I sold it all now.
Software, of course, is a write-off, although I got Sonar by paying the really cheap upgrade price based on some low level Cakewalk software I got packaged with my first interface (Aardvark Q10) that is now long gone.
All in all, I figure if I had to liquidate everything and wasn't in a hurry, I'd be about even.