I personally agree with holding out. Just because it doesn't sell fast doesn't mean it isn't going to sell at all. In just pure and simple numbers there are few people that are browsing with £7K burning a hole in their pocket.
But there are some, and if I was looking for a machine of that line of cost, MM, old or not, is a machine that's up there for consideration with any NIB game on my list, and the 'old' bit is less important when it's a clean, renovated example. Even against the remake it has the advantage of being The Original(tm) which matters a LOT to some people, letting aside the prior mentions about how those sorts of people will quibble about the trim, and it's a known quantity - MMR is still a bit of a unknown and I've heard the beginning of the scary rumors and gossip already - and let's not forget, underneath that playfield, MMR looks like this -
http://www.planetarypinball.com/wp-content/uploads/2014/08/MM-PreProPFBot.jpg - in my eyes that's an easy point to the original.
All depends on how long you're prepared to wait to find a buyer, or how desperate you are for the cash injection.
I don't honestly think you're going to get the price you want even after xmas. Prices for TAF seem to go crazy on the run up to xmas so I don't think it's that people with £7k to spend on a pinball machine are waiting until after xmas. If anything they want it before xmas so family can play.
That's a very fair point. The only alternative angle to that I could see is that TAF is The Special Pin That Everybody Knows. Non-pinheads I could see randomly splashing out for that as a Christmas bombshell, whereas the pinheads that would hunt down a MM I would equate to being a mix of people with a ton of money to burn at all times, or people like the rest of us here, nursing an expensive addiction that is being chained up and restrained until the xmas period is done with...
Or that could just be a load of shee-ite and people are just spending elsewhere.