Just curious, but what makes spikes lowers so popular? Like why do people pay such a premium for them?
What makes you say that people are paying a premium for them?
At around $100-120 a lower, they are what I think are about right in terms of stripped lowers that are available locally. Yeah, you see sales for stripped lowers online for much less, but then you have to add in shipping and FFL fees. I've even considered buying a bunch (like 10 or more) the last time I saw a sale on stripped lowers for Aero and Andersen in the $50-60 range.
I haven't built a lower from a Spikes, but I've heard that they are good. I think as long as you stay with known quality manufacturers, there's not much difference. That is unless you are looking for something like a billet receiver or one of those with the trigger guard machined into the lower. I have a Noveske billet lower that I paid a premium for, but Noveske stuff generally demands a premium.
Interesting that the only lower I've actually had a problem with is one from Daniel Defense. The hole for the grip bolt was off. It would fit with the A2 stock grip that came with it, but it wouldn't fit with any of my many Tango Down grips or even A2 grips off of other guns (Colt, BCM, LMT, etc). I eventually sent it back to DD for inspection and with the Tango Down grip that wouldn't fit. They sent it back with both the hole in the lower and the grip filed (bubba'ed fix) slightly and they called it good, but the grip still didn't fit properly (it had some tilt). Anyways, that sort of ruined it for me and I ended up selling that gun off to a friend for a good price.