What's 500 neopoints worth?
You might think, why would you waste the time to do an auction or a trade, all the time and effort, only to make 500 points? Well, think about it. How long did it take you to do it? Maybe 30 seconds at the most. If you count the bidding time, and the time it takes to put it in your shop. 30 seconds.
Now think about that, 500 points in 30 seconds, that's 1000 points per minute, that's 60,000 points an hour. Granted some minutes you will make more, some minutes you will make less. You could be wasting time chatting or sending personal "neomails" . . . but in general, never pass up an opportunity to make money.
I've done trades and auctions to profit only 50 points. This was on scratchcards, where the profit was still 5%. I try to have at least a 5% profit on each deal, unless I know it's a "sure sale". Like buying an unbuyable paint brush for 98k. You know you can get at least 100k, so the 5% profit rule doesn't apply.
So just ask yourself, what's 500 neopoints worth? Is it worth your time? Most times, yes, unless it's not 5% of the amount you are putting out.