I think the issue with the card is and always has been there are other better options.
Tinker is generally considered better for above stated reasons. But it is restricted, so let's say you want 2? It feels as if most people would sooner play Tezz1, Mystical tutor for Tinker, Demonic tutor for tinker, etc since those cards not only provide more versatility than just being tinker number 2, but are also way easier on your mana base as opposed to the UU needed for Transmute (plus the difference you may have to pay.)
The fact is that Tinker is a shockingly powerful card that ends the game when it's played a fair portion of the time, so you really do not want more than 1. It is also very vulnerable to a number of answers and therefore can be a liability against some decks even at 1.
The good news is that the 150-200 dollar price tag it is holding right now is stemming from Commander where Tinker is banned and Transmute will likely remain an amazing card and keep the price and usage elevated.