If you're going to hijack someone else' listing, you should at least know how Amazon's buy-box works:
As long as the price is around the same, Amazon will rotate the buy-box evenly among the sellers.
If you drop the price drastically, you force the other sellers into a price war and your profits - as well as everyone's - will suffer.
You're doing the damage item. If you want to sell products and gained very little. You should list yourself!!
I sent an email to the seller who drop the price, and everyone is well aware of this. Has no insolence like you.
The action that such insolence will allow you to sell on Amazon not too longer.