They probably don't get an exact price, because there is no exact price. Prices change all the time and the price is always dependant on how badly the buy needs it how much the seller wants to get rid of it. Sheep has a price guide, though I'm assuming that will soon need to be remade by someone else as Sheep has resigned/left.
If someone asks for a price and they get answered "5-8m" instead of just "7m" perhaps they should just check the trading post themselves instead of asking for prices if they are expecting exact numbers.
Omicron was working on a system back at the end of 2017 I believe, but he decided not to continue with it. I would much prefer having this system actually working and fixed instead of a command just simply showing the lowest priced item.