$50-60 might be reasonable for the purchaser, but wouldn't be worth the time of the machinist. Most barrel shrouds are that much and they are primarily just turned on a lathe and then have holes drilled in them. This would require CNC mill time and much more time, at that. The only way to get the price into your "reasonable" range would be to mold the parts and sell thousands of them. I would look at adapting an AK or shotgun part and using a normal AR buffer tube instead of trying to reattach the plastic tube.