The trouble is sellers take too much notice of previous auction results, in particular the ones with daft prices and price guides which are either out of date or do not reflect a real world price. These days when something fetches a daft price it is then used as a bench mark and people want those prices for themselves. Some buyers paying over the odds for records that are in the main in poor condition. Sellers also want Mint/Ex prices for records in Vg/Vg+ condition.
The record collecting scene has been for years like the housing market, over inflated, sometimes falsely inflated prices and a crash is sure to happen at some point. Most of the long time collectors aren't getting any younger and with collections worth in many cases tens of 100's of pounds then many will look to off-load at some point.
Buyers are as much to blame, paying well over the odds when a quick search will often result in a cheaper copy, buyers paying top whack for a record they know full well the seller has quantity