We have had a hard top one for about 6 years, but it was given to us by a friend, who no longer needed it. So, I can't account for the value/price. We use it all the time! We put the suitcases in it for a family of 6. We have never had any leaks, etc. There is a certain amount of "drag", but I wouldn't say it's so noticable that it makes a huge difference in gas economy. If you are basically just going from point A to point B, maybe the soft would be ok. However, I can tell you that in nearly all trips, for one reason or another, we've had to get into the carrier to get something. Unwrapping the tarp to get to the item and having to wrap it all back up again, may be a hassle. As far as the price, you could look on craigslist, to see if there's one available there.
To answer the question regarding keys, etc. - we have stayed in hotels with the carrier. There are keys, but we always take the stuff in, anyway-even if we didn't need it with us. They are pretty indestructable, being made of fiberglass, but if someone wants in, they're gonna get into it.
Good luck in your search!!