depends, just the pair of TBs alone, with no sensors, no management, no fuel rail, no injectors, no manifolds, no nothing can be as low as 125 quid.
But,a full kit say the weber alpha gold kit is just about 2k for the lot fitted, then another say 400-500 quid for mapping time.
They really are one of the best things.
Everybody used to stick on twin 40s, but why do people stop, why not do the same qith the equivalent with some TBs.....far better than stock inj, and you can run a lumpier cam as you can map it far tighter