I really like this one: it has a full length zipper, instead of having to stuff/slide your spars and mast into a bag, the full length zipper makes it really simple and easy.
I can actually fit both my Sunfish and Minifish rigs in a single spar bag.
You can't make one cheaper. I'm in the marine canvas business and made one out of scraps. The zipper is $15 and it took about an hour to make. Nylon won't sit out in the sun, but you can beat the price.
This is the one I sewed...minimal tie-down when on the road and I"ve gone 65mph without worries. There's only one pic, where it shows the boat tied to the trailer...but it's one easy line...secures the tiller, spars and holds the boat to the trailer. I didn't use a zipper, so it could drain....and used "twist lock" fasteners (aka "common sense" fasteners). I use my bow line (or painter), to secure the front of the sailbag and spars...and use the bow handle and the mainhalyard cleat etc.
I've purchased their deck covers (the less expensive fabric). They were great deck covers. I used to sell spar bags myself. My cost was $40 then the price went up, so Intensity's $55 is not a bad deal and I have one of those for myself now. Someone sells deck covers and spar bags on eBay as well. Not familiar with those.