Years ago I bought Glock 21 mags for $75. $79 isn't too bad.
Gen 3 mags? There are drop free and non drop free and there are variants that have an extra part over the mag base with a key and hole in the mag base that make them harder to take apart.
Bottom line is Glock mags are Glock mags. Factory. Even drop free mags, often, will not drop out of a Glock like a Colt mag when you hit the release. You have to plan and expect a tactical mag extraction.
I have a lot of Glocks and various mags. All are equally reliable. I stake my life on them every day.
Best deal is $65. Good luck finding that deal. If the ban goes away, we will all be able to buy Glock mags wholesale for $25 again. I got some Glock 22 mags from some folks in Arkansas, recently for the magic $65, FML DF type. I figure many "investors" are dumping their mags in the event the ban goes away. Some idiots are still trying to get $120 for mags. We will all remember them farkers!