1500 all in a realistic price for a complete secondhand TB setup IMHO, in fact ive seen them go for 1200 in the past. On a standard XE the basemap is actually really good if you are getting a pukka setup, there is little point getting it mapped at all providing you can at least det check it and whack a wideband on to check the fuelling

Carbs you are looking at 600 for the carbs and manifold, then you need mappable ignition on top of that which is going to be best part of 300 quid including the loom so within a few hundred quid of what you can get the TB setup for, and on the carbs you WILL need a setup unless you get mega lucky and buy a complete setup off a standard XE thats already just been recently setup, which is actually relatively unlikely.

The cost difference is next to naff all in reality!