I have provided a suggestion on this earlier in previous threads, so will keep it short.

Auction value setting is determined by a range of player quality, by 90%+, 80%-89%, 70%-79%, 60%-69% & 60%-. Down-clicks (dc) refer to 5% less from max value.
90%+: max
80-89%: 2 dc from max
70-79%: 4 dc from max
60-69%: 7 dc from max
60%-: sell immediately

If set at the right price, players will be sold automatically by 3 hours max. Tried with every range with confidence.