There is a gal named Linda Long that makes some that are close to the shoo fly's but much cheaper. I bought mine 3 years ago and still use them. I believe she's from Iowa.
I have bought some of the cheap ones and had good results. Last winter, I got an amazing deal (I think less than $20 a set. WOW.) on some sets of Amigo brand boots and really like them. https://www.horseloverz.com/fly-insect-control/fly-leg-wraps/amigo-flyboots I also got a set of some brand I don't know in a box of tack I bought and they are working really well on my boyfriend's horses. He gave a pair to each of his geldings and they have really slowed down the stomping. Some of the super cheap ones have to be readjusted daily but I like to take them off and check legs regularly anyway. My horses are pastured so they get grass inside the boots but they aren't stomping their shoes off so it's a win.
I have used the shooflys and love them. that being said, for the price Im really disappointed they only last a year at best. I recently ordered 'stomp stoppers', which are very similar but they are much more durable. Id recommend either of those 2.
Shoo Fly. They have been protecting my horses' legs all summer and still in good shape. A friend of mine bought hers last year and I noticed they are still in good shape this year. That's what convinced me to spend the money on them.