If you're not opposed to it, you can use the $5 cert to get a $10 PSN/eShop card. That's what I do every month. So far $20 PSN and $10 eShop for $15 out of my pocket, and used PUR points to pay for my membership. It's not great but it gets me digital money for half price.
Oh, that's absolutely the plan- it's just the hassle of actually making a trip to the Gamestop once a month to do the buying. Unless it works online? I'm still trying to figure out exactly how the thing works & Gamestop's customer service is completely useless.
I've used point to renew my membership for years, so I'm not out anything from my pocket- but without the used game boost earning me more points from friends, I imagine I'll be running out in a year or two- and when that happens I doubt I'll renew. This new thing really doesn't work for me.
Anyway, on topic- I have the same problem every Amazon B2G1... they won't put 3 games I want on the sale at the same time! It rotates around my wishlist, but never more than 2 at once. It can be annoying, but at least it saves me money from not buying anything.