Gee, for the record, I don't see anything wrong with inline skating for fitness. I've run quite a few miles on the lake fitness trails in Minneapolis, and they seem like great sites. In my hockey days, I considered getting inline skates, but figured I'd already spent enough $ on the hockey gear, and I didn't have any convenient locations.
If it's anything like hockey skates, you'll almost surely have to spend over $100 for a pair. I wouldn't be surprised if the high-end stuff got up in the $300-400 range, but that could be overkill. I'd look at shops that have some kind of in-line specialty/expertise, rather than box stores: they'll have higher-quality gear, and the employees will be way more helpful and will make sure you buy the right size .