Buying raw cards online

[ASF123]

Hi, and I apologize for another "advice for the new guy" question...

I've now received a decent number (nowhere near all, thanks USPS) of the cards from my first round of eBay purchases after coming back to the hobby. These include a bunch of raw '50s/'60s HOFers. It seems like one big takeaway is that one should probably never pay more than about a PSA 4 price (per VCP) for a raw card on eBay, regardless of how nice it looks in the photo/scan (and, of course, how it is described).

Reasons:

(1) If it was really a high-grade card, chances are good that someone would have had it graded at some point;

(2) Let's face it, PSA is arbitrary and subjective. There's nothing "real" about whether a card is minty enough for an 8, minty enough for a 7, or not quite minty enough. It's just one person's opinion on a given day.

(3) Given (2), it's impossible to predict whether a given raw card would be, say, a 5, 6 or 7. And it's even more impossible to do so based on a few photos online.

(4) Given (2) and (3) plus all the bad incentives inherent in PSA's business model, it's unlikely that a card submitted by a random guy like me would get a very high grade, even if it was probably worthy.

(5) TPGs seem to exist basically to sh*t on really nice-looking cards. I now have a couple of PSA 4s that would have easily been sold as NM 30 years ago, back when everyone was happier about the condition of their cards .

So, is the "nicest card I can find for around PSA 4 price" policy on the right track? It's going to shut me out on a lot of cards, I'm afraid, as people seem to have no problem bidding up the really good looking-ones (esp. on Greg Morris). But it seems like the prudent way to go - the few times thus far I've won an auction at like a PSA 6 price, I've ended up irritated by a flaw that was more noticeable in person.

I'm not really trying to invest per se, I just don't want to spend a bunch of money on cards that won't hold their value at all. Of course, some appreciation would be nice.

Thanks in advance for any discussion...