I have a customer, really cool guy in his mid 70s, with a pair of 1970s Nortons he keeps in his backyard exposed to the elements. It's a small yard and a tight squeeze back there.
$1,500 seems ridiculous when you can get those fabric flippy covers for $310 USD. I've recommended he buy a couple of these:
Water-Repellent Flip-Over Motorcycle Tent
Another advantage of this setup is you build a 2x8 frame for the bottom and tuck your M/C lift underneath the floor. It has worked well for me for the past 8 years.