That might be a ridiculous price by 30 year old standards, but it's really not that out of line. I bought my last topper in 2013, and I think I paid about $1300 for it. It's fiberglass, with a headliner and glass windows that open both as a door and as a sliding window.
An aluminum topper with no options would be cheaper of course, so it depends on what you are looking for.
It seems to me that an inflatable topper will be pretty nichey and low volume, which would push the costs up. So ~$2000 now doesn't seem ridiculous for what it is.
That said, I don't think I'd want one, especially at that price. While it would be nice to be able to install and remove it without help, my topper stays on almost all the time, so that's not such a big deal. And with it on all the time I'd prefer the looks (and likely the durability) of a fiberglass topper.
Still, it's a cool idea!
Bob
Sorry, no '80 - '86 Ford trucks
"Oswald": 1997 F-250HD crew cab short box, 460, E4OD, 4.10 gears
"Pluto": 1971 Bronco, 302, NV3550 5 speed, Atlas 4.3:1 transfer case, 33" tires
"the motorhome": 2015 E-450-based 28' class C motorhome, 6.8L V-10
"the Dodge": 2007 Dodge 2500, 6.7L Cummins