Rewards programs that pay out in store credit, what do you buy to resell?

I currently have $350 at Amazon, $112 at Tik, Google $149 and various others at $0-200+. There aren't any ways to cash out for money directly and am curious what people are doing with them. It seems worth doing but I am noticing as my balance grows higher I don't really have much to buy at those stores. Gift cards are easy enough to move thankfully.