I find that high value items, at release, tend to halve in value (or maybe quarter?) each time one sells until it hits a stable point. So, there will be 1 listed at 10m that sells, then 5 more go up for 10m and none sell. Then someone lists it at 5m, or undercutting brings it down to 5m, and then another sells. And then it drops down to 2m before selling again. Unless supply is extremely limited such that only about one of the item per week appears on the MB, or the item costs a lot to make.

And then there are other factors. Back when someone figured out the gardening recipe for Blood Peppers, I grew as many as I could as fast as I could with only five gardens to work with. The minute I obtained some, I knew the supply was about to spike as other gardeners found out and shifted their gardens to growing Blood Peppers. So, even though they had been selling for like 2m, I listed mine at 500k, and when someone undercut, dropped it to 300k super fast. Someone undercut me again, I put them down to 200k. And I sold my whole first batch, and second, before the other growers' supply got such that their value dropped to 50k. If I had kept trying to sell at 2m, they wouldn't have sold, and then the value would have tanked and I would have gained nothing.

If you stubbornly keep your prices high with zero sales, you're not being a good businesswoman no matter what you think about undercutting.