According to my data there have been 99 turntables moved for museum or tourist line use, not counting the one at Ridgeley, WV, just discovered by posted photos. Of these 36 are in use, 54 are stored, and nine have been scrapped. Of these 18 have been moved twice and three moved three times. Some have moved with their owner's operation, some between them. The main reason for so many in storage is exactly the high cost of building a pit and the center pivot point to make them usable. The cost varies based on the specific piece of land involved and engineering costs to determine the way to build the pivot and pit are part of the cost. One of the reasons that the one installed at Steamtown before moving to Scranton was rarely used was that the pivot support wasn't built properly and it shifted every time the turntable was used. The contractor did it cheaply and it didn't work out well. So saving money on this was isn't the way to go for anyone thinking of installing one. Here is what the Railroader's Memorial Museum in Altoona publicly reported spending to install theirs:

2006 – Railroaders Heritage Corp/Altoona Railroaders Memorial Museum in Altoona, PA, was building the pit for installation of their 105’ former RF&P turntable. To July $815,000 had been spent in addition to acquisition cost for the turntable and shipping it to PA. These are $95,000 for soil boring and engineering, $640,000 for the foundation work, $12,000 for caissons and related engineering, and $68,000 for track construction in the turntable area.

My data is limited to info on moved turntables, although I do list 23 in use that haven't been moved as the group took over an existing railroad roundhouse with one or a similar turntable to use. I do have the info about the moves of the ones at the Reader RR and Eureka Springs listed. I'll be glad to share the listing with anyone interested if you send me your e-mail address by PM. I've sent it to three people in the last few days. I keep changing it as info comes to me and just yesterday added this:

2014 – The A 75’ Bangor & Aroostook turntable at the former tourist line in Unity, ME, has been dismantled for shipment to the Smoky Mountain RR in North Carolina. It is expected to be used eventually in Dillsboro, NC. This is its second move.

So this list is always a project under revision, with corrections and additions welcome.