I do it cus it's what the veterans do. Some remove the pics too and even all the info. Sites like bay and etsy do it too -- remove the final sell price.
I dunno. Maybe so noobs can't be like, 'This one sold for $200, so why are you asking $800 for the same item'? Because that $200 sale thread is 15 years old...noob. Just a guess. Really no idea.
Ebay doesn't. You often see "sold for XX", and you can check the full bidding history on auctions.
All the arguments for removing the prices are weak nonsense. Such as the claims of harassment weeks or months later: If you put SOLD next to the price, it has no reason to happen, ever. That is exactly the caliber of argument in favour of removing the price.
People like to remove the price because if you allow them to express their natural cheapsakeness, they scramble to act on it.
Gaston