PSA goes after the market aggressively, that's why their "sale" prices "look" cheap, whereas other brands, like SA, do the usual MSRP route. But, you're getting a quality gun from PSA who pursues a different business model that the typical AR manufacturer.
IMO, with some brands you pay for the name vs. what you're actually getting as far as features.
One needs to look at what the factory rifle is built with when it comes to the barrel, BCG & trigger which are all my key elements when building a rifle.
While I prefer a CHF CL or SS barrel I do have a couple of nitrided barreled uppers (PSA) if they fit a build-need. BTW - I do have a PSA upper like the one in the first rifle choice on Page 1. It's fine.
It's very hard to beat a PSA upper with a FN CHF CL barrel that's on sale. Especially like this one, if you want to go with the 20" barrel & A4/A5 configuration.
Here, the sale price covers the cost of a FN barrel & you're getting the rest of the upper for free. But you still have to get a quality BCG & CH but PSA has really good deals on BCGs and lowers if you're not in a hurry.
But, the PSA shown on page one is a good deal for a starter AR, especially if that's all the configuration you need..
BTW - I've never had/used a bad PSA upper/lower & BCG. Plus, PSA has as good a warranty as anyone else.
HGs recommendation of looking for "blems" is a good one & you may have a tough time finding the "blem". IMO, other brands just ship out what they "assemble" and wait for a customer to return something that looks "blemmy".
As HaysG says piston guns are pricier but are very clean to shoot. I just put a PWS Mk. 118 MOS 2 upper on a YHM lower build & it's very nice, BUT I may end up getting a stripped PWS Mk.1 MOD 2 lower and build that up to the standard I do with all my Tier 1/2 builds to make it an "all PWS" gun.
My .02