I own a Squier Affinity P. Got it used for free. It came in pieces and I had to refinish and assemble it. I love it!
Now, I have been a musician and guitar player for well over 20 years. I've also been a guitar tech for about 14 years. I've played many different guitars, some cheap, some worth a whole lot of dough. I know a quality instrument when I see one.
First off, no, the build quality of my Squier is not equal to that of a MIA. The bridge and tuners are cheap, but they do their job. The pots are cheap, but they work fine and make no noise when I turn them. The pickup, while it doesn't say Fnder on it anywhere, works just fine, and sounds great.
I've said all that to say this: Yes, there ARE huge quality differences between a MIA and a Squier, but......
After a pro set up( level, crown and polish frets, adjust relief, adjust action, adjust pup height, intonate, ) the guitar plays and sounds just as good as any instrument, no matter the price, that I have ever played. Period. Is it the equal of a MIa, or even a MIM in terms of quality? No. But it sounds and plays every bit as good as any of them you'll ever pick up. And that's the bottom line.
I don't see anything wrong with people paying whatever they want to in order to get the best quality they can afford. If I were honest and had the cash, I'd tell you that I would definately own and play a MIA. No question. But the bass I own now, as far as playability and tone, IS equal to them. As far as build quality, fit and finish goes, most non musicians would not know the differences unless pointed out to them. But they are DEFINATELY there. However, when I play other basses, my Squier is the yardstick I measure them by. If they do not meet or exceed that standard, they're not worth my time. There's a lot said just in that sentence alone.