Difference in price could be due to many things which include thickness and bonding techniques for the seams. Of course there is always the big PROFIT variable. On solar covers in general, consider getting 3 years as gravy. Usually they start getting brittle from the chemicals and sun exposure and the bubbles break. When one has reached end-of-life as the primary cover, I cut it up and use good pieces to cover areas in my oval that the single rectangular won't cover. Pieces are also good cushions on concrete deck for laying the rolled up cover.
Al