What the heck is this thing?!?

[The Torii Fox]

So we took in a cat a couple years ago, and for a series of reasons I have very little interaction with it. My wife got her spayed and all the other normal vet stuff done, and we took her in earlier this year I think and got her some dental work (a pretty nasty abcess). She is an outdoor cat 90% of the time. Long story short, I just noticed this thing on her ear earlier this week. My wife said she's been telling me about it for a while but I don't remember (insert marriage jokes here). We are making an appointment to the vet but I would like any insight as to what it might be, and if someone can ballpark the cost of treatment so I can prepare that would also be very helpful. Thanks in advance for any information.