BKC,
To each their own. As you know your horse will let you know if something is wrong. The mountain trails I ride are rock-on-rock. I am sure there are some hard-feet horses that would do OK, but I am not risking it, and I haven't had a problem. The additional traction from borium shoes up front is super nice during the late season.
As far as expense, it runs about 90 buck a change, which is an expense, but so is pasture, feed, vet, tack, trailer, etc. No matter what you get into a horse for, none of them are cheap.