One more note about the Retrax (and likely other covers from Truck Hero, parent company of a gazillion brands including BAK, Roll-n-Lock, Extang, etc.): I recently learned that they have minimum advertised price (MAP) policies, so you won't often see discounts. However, with a little work, you can get a discount.
I got $270 off my RetraxPro XR (about 13%), but since I ordered, I heard you might be able to get 20% off (that would have saved me nearly $400). So, first just ask for the discount via chat or phone. You might get it. If not, find a site that will give a discounted quote via email. Then, either order from them, or request a price match from your preferred retailer. That's what I did to get the $270 discount, but it seems you can do better, so first just ask for a discount.
Still pricey, but this makes it a little less so.