With some lower receivers, the PMags can be tight and not "pop" out when you hit the mag release. This is the way it is with my Mega Gator lower. It's not a strugle to get them out though, I just have to use my hand to remove the mag. Basically I can't hit the mag release and have them drop out on their own, there's enough friction there holding them from doing that. After enough use I suspect they will drop free for me, because they are getting easier and easier to pull out the more I use them.
As for cost, just be thankful you don't live here in Cali like me. I can buy straight 10 round mags which suck to get a grip on for around $11, or I can buy mags in 20 or 30 round bodies that are blocked to only accept 10 rounds. But these mags cost $25-30. It hurts everytime I go onto the EE mag section and see 30 round PMags selling for like $13 and knowing I have to pay 2.5 times that to get the same mags and they only accept 1/3 of the rounds...
I envy you and your strugle over spending 1/2 of what I have to pay.