I'll have a go at answering this.
It depends on:
how much I paid for it and how much profit I think I need to make.
I don't automatically go "this record is worth £100 so I'll ask £100".
For instance, had a Jimmy Beaumont on my list yesterday, it cost me £60. I listed it at £90 which I thought was a pretty good price for a minter, it "books" at £100 and £150. £30 is a good enough profit. Towards the end of the day, it hadn't sold, someone offered me £75 so I took it. So only £15 profit but at the end of the day, I just can't afford to have paid money for records and not sell them.
The men with the finance and years of doing this can do because they have financial security, it doesn't matter to them if an item sells or not, they just bring another one out.
This is a matter of - well not life and death but it's serious for me - one income in the house, baby arriving next week, and the only income is that from records so it's finely balanced, I have to make sure that the records are priced attractively enough to undercut everyone else whenever possible and are priced to sell.
When I get something that I know really is rare, I'll ask for a decent price for it - yesterday, Linda & The Pretenders at £500, I know this has sold for £800 but who's got that sort of money at the moment?
When I first started this I was doing very, very well because the bank supported me and gave me a £5000 overdraft which I used to buy as many records as possible. Since I moved back here, I have no overdraft at all, so no spending power, hence I have to spend most of my time trawling ebay to find bargains.
But the point is - I think if I had the financial backing again, maybe I';d get that old attitude back and think about putting prices UP because it doesn't hurt if the records don't sell so much as it does now.