Should I buy an SME 30/12A for 15K?

Until you know what cartridge and phono amp the dealer demoed the SME with, you cannot know how the SME sounds in your rig. $15k is enough to ask the dealer over to demo it in your place.

Come to think of it, we don't know what cartridge and phono stage you are using. 

100 albums? And you want to spend 15k on a TT? Nope not worth it IMHO

Has the Collection of 100 Albums been collected over the past two years.

Have you bought Individual Albums or some Batched/Job Lot deals and are they New.

I am going to assume, and happy to be corrected if inaccurate, about your purchases of Albums.

Have the accumulated 100 Albums been purchased as Individual New Items over the past Two Years ? In my assessment in the present Marketplace, the cost for such Source Material will be close to $2500 for the Items without Shipping Costs. This is a Big Commitment by a Hobbyist, when there is other Recorded Source Material available most likely of the same recordings, that can be attained at lesser outlay, especially as you have a investment in Digital already. 

I have heard a Digital Set Up used in a Predominantly Vinyl Source System, that has a New Purchase Price of approx' £5K present itself as very attractive as a comparison to the Vinyl Set Up with a New Purchase Price of approx' £25K.

Getting the absolute best from Vinyl using the Mainstream Brands as either Used or New Purchases can accumulate to substantially more in costs that creating as a attractive presentation using Digital as the Source Material.  

I am a little like your approach to the Vinyl LP as a Source in relation to the Digital Source. I have not too long been into Digital and have created a Digital Set Up in the main system only a few years ago. I had to purchase CD's as the only ones available were used in a Car or a few of my Son's Gangsta Rap type of genre.

The Digital Set Up put together with very limited investigation and experience, even though guided by some who are experienced in Digital,  has created a Source that integrated into my System very well, it is very attractive to have musical encounters with, and it has been used in place of the Vinyl Set Up on numerous occasions. 

If you don’t buy that table can you give me the dealer information? I will buy it in a heartbeat!