Are people just not paying attention or is there a reason behund this?

I imagine questions like this appear on the forums fairly regularly, but was wondering if anyone had insight into this approach to undercutting:
The buy price for this item was at 2.2mil last night, and i sold a good 30 or so units of it at 7mil, and since then 26 more have been posted for sale at less than half the price.
If it was an item that moved slowly, so the person selling wanted to make a quick buck I would get it, but it really isn’t that kind of item.
And it’s not like they’re undercutting another nearby station - they seem to have just picked a randomly low price.
As soon as I have enough sat in my wallet I’ll just buy them all out and repost at 7mil I guess.

Any insights into why people would do this?

Average that sell window puts in as default price for sell order? When you have set up something more than instant time you end up with absurd orders on market.

Some people don’t pay attention to this and game sometimes put absurd numbers there.

They might not want to play the 0.01 ISK game, and would rather sell at 3.1 M than be undercut and not sell anything at 7 M. Your post is proof that their strategy is working.

Sometimes people who want to buy a large quantity will post a sell order for a small quantity at the price they want to pay hoping that the next person to list will undercut them - market PVP. Sometimes it’s just carelessness, or they may simply be tidying up their hanger and want a quick sale. No way to know without asking them.

They undercut you and you did not retaliate - mission accomplished.
People usually have reasons for what they do, usually to either achieve short term, or long tern profit. The long term aspect can be that they want to free up money quickly, even willing to take a short term loss.
You have no idea of knowing if that was their thinking in this situation, you just have to accept that they have other priorities than yourself.