It’s possible because the system is bugged. There are three missives of mastery which have existed locked in at 40 gold since early Thursday. And then now since then there’s more locked into certain points, so when you go to buy you can’t buy the ones that are locked because technically they don’t exist in terms of you cannot purchase them. They are not available.
So you have to buy X amount to get to the first one which you can actually buy. Except the game doesn’t have the functionality to recognize the rest are broken beyond telling you that you cannot buy the ghost ones/bugged ones, so when you do reach the ones which truly exist, you are buying ALL the ones you had to enter beforehand to get to that price point.
If three are listed at 40g but don’t exist in truth.
If another forty exist at 55g but don’t exist in truth.
And the next listing is at 60g, and you only want to buy one you have to buy 44. 44-40 at the 55g, -3 at the 40g and then the one for the 60g one… except the game then buys 44 at 60g.
Yes, this has been bugged reported by many. And yes, unfortunately, there are many taking advantage of it.