Well you need ideally to put up some specs ( pump - lpm - etc ) £4K well they saw him coming didn't they, !
The pressure washer is worth around £600 - £800 depending on spec, service and use.
The flat service cleaner is a good one - mossmatic by the looks of it, personally I think they are well over priced from new but I suppose second hand you would get a good £500 for it.
So I'd be willing to pay £1k - but I would only be taking the FSC because it came with the pressure washer, I rarely use them, turbo nozzle for most work
Darran