I just had a place sell me a set of Magpul flip sights -I was in a hurry, but I thought at the time "Man, that's a GOOD price". Nope. About two miles down the road at a red light I was checking them out. They just didn't feel like the others I have. I noticed little fuzzy edges and other things that just looked wrong. Sure enough the Orange & Beige box had in TINY PRINT on the back "For Training and Simulation Use Only". Turned around and went back. They had a single Mbus Rear Sight on the wall and I bought it after getting refunded. I immediately opened it - yep - much heavier, clean and solid. The guy at the shop had this shruggy attitude while doing the refund. I'd said that I needed to return those and get sights for a real firearm. He was "No THESE are for real guns..." I pointed out the mice-type as he looked bored. He said "Well, we sell all of our ARs with those on them and no one complains - they're real sights." I said "No - they are toys - they are crap" and hit the door. Wow.
Spend the money. No, you don't have to buy those snobby three hundred dollar hand guards but don't - for cryin' out loud - put TOY parts on your firearms. Man how I hate that one industry with it's "realistic enough to get your ass shot by a cop" toy line. It's criminal that they can make and sell toy parts that imitate real items for real firearms. Newbies will buy them unwittingly, greedy store SOBs will sell them as real, cheapskates will reason that they are good enough and buy them - and someone will have them fail on a real firearm and maybe they die.
Spend. The. Money.