Lots of "depends on"...
The SME arm will generate quite a bit of interest, so will push the price to around the same as an LP12/Ittok, although IMO the SME is inferior to the Ittok on an LP12 (synergy, y'see).
Has the LP12 got a Valhalla power supply? It will have a black power button with a red LED in it. If it has a red square button, then it's a basic.
Also, the plinth colour affects price. The afromosia (teak) fluted design gets the highest prices.
So I would say that it (assuming that SME/Shure combo is in good nick) would start at around £600 for a black basic , rising to somewhere between £750-900 for a valhalla afromosia.
I sold my afro/valhalla/ittok for around £800 about 6 months ago, which I was happy with.