Hi there Popps!
The last taming Mark that I saw sell on Catskills went for upwards of 40 mil. This was some time ago, when I bought mine, it was closer to 60 mil.
However, regardless of the above costs, they so rarely show up on Catskills for sale. You would be much better off with some spare jewels that have taming/lore/vet. Honestly, it would be cheaper (and more likely) to get a ring brace set with +15 taming/lore/vet each and buy a Birds of Brit talisman than to obtain a taming mark of the travesty.
Of course, if you already have +15 taming/lore/vet jewels and a birds of brit talisman and still need the 20 extra points from the mark of the travesty me thinks you'll have to pay the piper, buy it on another shard and x-shard it over.
Of course I could be completely wrong and someone will post here selling one, though I hope that is the outcome I just wanted to give you an idea of what to expect.