I've been casually collecting Amiga gear for I guess a couple of years now and I've found the key at least in my local market seems to be lots of patience. I've only ever bought stuff off my local craigslist, the good thing here is stuff seems to be about 1/4 the price it would go for on ebay. The bad thing is an Amiga probably only pops up about once every 3 months. Though lucky for me it seems like I am pretty much the only local buyer within a populous of 2,000,000 so it hasn't been hard to snag anything I wanted yet.
Now I just gotta learn to resist buying stuff I don't really need dammit ... my basement is getting crowded with Amiga stuff. I thought I had almost everything I wanted but I couldn't stop helping myself to a nice A3000T with Picasso 4, Concierto, ethernet and an 040 that I picked up a few of days ago. I think I'll still look for a nice clean A3000D though. It's gonna be hard to resist more gear though if it comes up for rock bottom prices. I guess I'll hope for an 060 for less than $100 but chances of that are probably about 1% in my lifetime.