Can still be learned
Engineers with sufficient skill (250) can learn the Tranquil Mechanical Yeti schematic by completing a quest in Winterspring. You do not receive a schematic as a reward, so you can't sell it. Only your creations.
To start the quest chain, you must talk to Lilith the Lithe inside Everlook's auction house and follow the quest chain until you've accepted Seril's Boast quest.
After that you can begin the Are we there yeti? quest chain from Umi, which eventually leads to Yetiphobia. After it's completed, talk to Umi again to learn the schematic.
Tranquil Mechanical Yeti:
- 1 x Cured Rugged Hide
- 4 x Thorium Widget
- 2 x Globe of Water
- 2 x Truesilver Transformer
- 1 x Gold Power Core
- 1 x Cured Rugged Hide
- 12 x Thorium Bars
- 4 x Runecloth
- 2 x Globe of Water
- 4 x Truesilver Bar
- 4 x Elemental Earth
- 2 x Elemental Air
- 1 x Gold Bar
All companion pets are valuable and it's up to you and your competitors to decide the prices. Personally I sell yetis for about 2500-3000g and if someone else undercuts me a lot, I hold a pause and wait until the person has sold their yeti(s). 90% of the time they do not create any more and the market is again mine.. for a while.