For example here's a screenshot of the market history for PLEX in Domain.
Note the low prices on the dates 08-13 and 08-10 are 760 mil and 763 mil respectively. Yet when I look at my transaction log I can see I bought 5 on each those same dates for only 745 mil and 745.5 mil each.
Obviously price history is not a very accurate indication of what things actually sell for. So what is it then?
Market history does not show the prices things actually sell for. It seems to miss a lot of lower priced transactions (like my 10 PLEX above) which inflates the numbers meaning the prices things actually move at are often lower than market history indicates.
Maybe market history only uses sell orders without taking buy orders into account at all. That would certainly explain why my purchases (usually made with buy orders) are often lower than what market history says is the lowest price.
But that doesn't explain other inconsistencies in the history data, like how I sold 5 PLEX for 784 mil each on 08-13 when market history says the high price for that day was slightly less than that.
I know for a fact that on the 13th there were a whole lot of sell orders listed higher than 784 mil, many of them much higher so history can't be just taking periodic snapshots of listed sell orders as I first thought. That'd push the average way up.
Then again the average prices shown in my screenshots above are lower than I would have expected unless it IS taking buy orders into account too. But in that case why didn't my buy order purchases show up in the data?
Whatever the cause may be something funny is going on with market history. The problem is market history prices are often misleading, sometimes very misleading, especially for low volume items. In a worst case scenario, market history doesn't reflect anything near the real prices an item normally moves at but instead shows extremely overpriced listings that for the most part are NOT SELLING.
What I'd find a whole lot more useful than this is information on the prices things actually sell for. I'd much rather have accurate info on the prices (with volume numbers) something actually sold for than what someone listed it for.
On a related but slightly different note, in the case of PLEX I'd really like to see information on two specific things
1. How many PLEX were bought from CCP with real money.
2. How many PLEX were actually used (taken out of circulation and used for subs, transfers, etc).
Even yearly data on PLEX purchases and usage would be extremely useful though monthly data would be much better. No need to get fancy with in game statistics, regular reports or anything, a simple one time dev blog post containing the information would be just fine.