CopiaVita,
Prices have all come up with time and inflation, just like everything else, but spikes occur along the way, like now with the TV shows. Things like local seminars on Government auctions cause big attendance and price spikes. But, the hard working and persistent always prevail. My dad used to say "The hardest working people I know are also the luckiest."
Most of my experience is in live auctions of all kinds, not just storage units, and the biggest changes have come from the huge increase in information available to ascertain values, and the expanded venues to sell stuff. I started doing this before the Internet, and you had to dig up information the hard way by calling dealers and subscribing to publications that they advertised in. The ease of finding information has closed up the margins probably more than anything else.
One thing I like about storage auctions is that you have to use your experience and knowledge "on the fly" due to limited time and lack of ability to "inspect" the merchandise.
My motto for live auctions in general is "To get what you expect, INSPECT !!!"