Basically fitting all the bits and peices and making sure they work.
Installing mast and rigging and tuning it, connecting the lights, radio aerials etc up the mast and making sure they all work. Seeing that the engine runs properly and that the shaft is aligned so that it does not viabrate and that the boat goes into ahead when you put it in ahead, and not astern. Setting up the wind instruments, swinging the compass, making sur the water and fuel tanks do not leak, that the batteries are charge when the engine is running and so on.
It takes at leaast a couple of days to do properly and you need professional help for things like the rigging.
In Britain any item sold must be fit for purpose. In that case surely all the things that Chris says are part of the commissioning should already be done for FREE!
As an example, Dufour charge £3,200 for commissioning and £3,300 for delivery for a 36 foot boat.
That is a total of £6,500 to do work that you would expect to be included anyway and to drag the thing accross the channel! Good value for money I'm sure you'll agree.
Nothing gets done for free. Its just a simple matter of marketing pricing, split the price up and it looks more reasonable. I always ask for an all inclusive price before I buy anything & then negotiate on the components ... don't you? Why should'nt vendors play the same game?