I lived with a SOTA Cosmos mk3 for 2 years, then upgraded it to the mk4 status. I could hear the speed UN-stability it was playing with my records. Which is what drew the turntable out into critical listening for me. I could hear the speed change over various songs pretty easily. This turntable retails for over $6500 and it cannot even play a record consistently.
I wonder if it is the belt drive design. Regardless, the SOTA implementation of a belt drive is pretty poor. Compared to a vintage $300 Luxman PD-264 - a direct drive design sourced from Panasonic, this turntable plays at a far more consistent speed than the SOTA.
Have you heard a record played on a direct drive turntable vs a belt drive? I think the reason why you do not see direct drive turntables in the 'high end' world, is because Technics/Panasonic holds the patent for Quartz locked direct drive:
http://www.kabusa.com/ttdrive.htm
There is a link to explain in more detail the evolution of turntable drive design.
Where are the 'high end' direct drive tables? The Grand Prix Audio Monoco table is a new one. Brinkman has a direct drive table now called the Oasis. Hopefully we will see more.