I'm thinking it's something that might have to be manually set but rarely do I see IO's go as high as 10x their average sale price, even when they're low. That would still be a good prompt. This may be something that has to be done manually for a time until the system gets an overhaul. But that's in dreaming. I work the auction house repeatedly and only salvage has ever sold that high over it's average price. I've never seen regular, rare or even purple IO's go beyond 5x even when none were left. A few times things get up there, 2-3x but never higher than that. So a warning prompt for a manually set price if it goes over, might be easiest for the Dev team as well. It'll have to be updated once in a while but that does give it a lot of leeway.
It shouldn't be informative of the average price either but just stating "This is an error prevention warning for accidental overspending" etc.
Wouldn't help much if you mess up on purple prices as they're already so costly. 10x is still a high price, but it will help prevent major loses on yellows/oranges and salvage material.
My concern is that with how the game lags, when it does can lead to some funky things and always has. I've messed up overpaying many, many times before and have lost billions back in may>september. I was also under the impression things were being worked on and fixed so I'm just adding to the queue if it isn't already in there.