If it’s truly over $400 to shrinkwrap, I’d rather pay slightly more to have it inside solely for the peace of mind. A fishing boat can be stored in my area for $500 in a pole building. My tritoon is inside an unheated shed with concrete floors and it’s own cover on it. My fishing boat is in my unheated (but insulated) garage with nothing on it. I’ll toss the cover over it if I’m cleaning or doing wood work to keep dust out.
Boats aren’t getting any cheaper. A roof overhead may not offer any more protection, but it does give me fewer worries than a tarp, shrinkwrap, or whatever else goes with storing it outside in the elements.