Tony I understand the exact question your asking because I asked it of myself the other day. Why buy a $3-350 Seiko when the rep PO 42mm I'm currently wearing looks/feels/appears to be of at least the same quality of the Seiko SKX-171 it replaced?
I have to say that if you look at the rep as *just* a watch and ignore the fact that it's a rep it's still a fairly high quality timepeice. For example the bracelet on the rep PO (5th gen) that I'm wearing is at least of equal quality and construction of a comparable Seiko, hell this rep has SEL's whereas Seiko only has hollow end links until you spend quite a bit more money. Same for the crystal, if indeed it is sapphire (which I'm not going to destructively test to find out), this again is a great value for money as no price comparable gen from Seiko/Citizen will typically offer sapphire. As for the movement, well I have the 21j DG4813 which from what I can tell is a rep of the Miyota 8125, I've had gen watches with the Miyota movement (LACO Fliger) that cost more than the rep does so what does that tell you -- you can pay more for a gen and get what is the same movement as a rep? Seems like the gen watch isn't as good of a value really.
I have to disagree, you can get a Seiko 7s26 powered automatic for $300 or less all day long and I'd say that the 7s26 movement is probably better than most rep movements based on price. If I could have ordered my PO rep with a new, adjusted, 7s26 I would have in a heartbeat because I know that the Seiko movement is a reliable workhorse that will likely outlast the rep movement.
Heck, you can pick up several Orient's for under $100 with an in-house automatic movement that are excellent. $300 does not mean quartz at all, $300 can get you a very nice gen with an auto no sweat.