TL;DR but:
I am a vintage set builder. I like nice quality cards, but I am not a high roller, so I want to do stay within my budget. When I start a set, I pull down the checklist and add in the Beckett book values, which I use as my guide for bidding. I normally looked to get EX-NRMT cards at 35-40% of Beckett high book value and go down from there for lower quality. Over time, I've limited my sources of cards to local shows and Greg Morris' Ebay auctions. That's it. I've dropped all other on-line sellers.
So, I have a few observations about Greg Morris:
- He tends to grade conservatively. I will actually bid on cards he grades at VG-EX because they tend to be of equivalent to other sellers EX+ cards.
- I used to clean up on his auctions using my 35-40% rule. Over the last year, this has changed. Where I used to get 10-15 cards in a particularly set break, I now get 2-4 and cards are selling way, way above what I am comfortable buying at.
- Yes, I ended that sentence with a preposition.
- On a related note, when I put together my 1955 Topps checklist a couple years ago, Beckett listed the Clemente RC at a book value of $2,200. When I looked the other day, it was up to $5,000.
- My conclusion is that we are in a market bubble right now and auction results are just way out of line with longer term trends and what we have come to expect having been in the hobby for a long time.
YMMV