Theyre quite expensive, if it was really a big deal, I think I would just use a diesel generator + electric fan heater. bit of a bodge, but saves you £1500-2000 surely?!
Depends a great deal on which 34' boat, cost for installing carefully and unobtrusively with the outlets in the right places and not just taking the course of least resistance as so many appear to be done can vary wildly due to disassembly and reassembly with care and without damage. Number and particularly positioning of vents also varies and can affect costs. Generally speaking a 34' boat does need something like 3.5 kw to be properly comfortable and almost silent once up to temperature using fresh rather than stale moisture laden air. The heater will run hard and be noisier (thought not overly so if silenced) and then ramp down to maintain the temperature which is what they are designed to do and using a modern heater and current ULSD fuels this is not an issue at all as it was in the past. It is important to understand an owners expectations before embarking on an install as much as any other factor. But to answer the OPs question with the above reservations. for a straight forward install the supposed "offer" of 2.5k at the boat show seems about right and around what I would normally charge for a simple two outlet install to Webasto protocols with three year warranty including duct silencing & lagging but excluding any travel and major dismantling.
