Who is doing the survey, how far does he have to drive, when does it need to be done by, what are his liabilities under state law, how detailed is he. Many of these have no bearing on how long a survey may take, or the cost to him of doing it. For instance, a visual inspection of the rigging on any sloop is probably going to take about the same length of time. However dye testing each fitting on a rig is more dependent on the size of the rig.
Frankly I can't figure out why people think a smaller boat is going to be much less time intensive to survey, assuming the same detail of survey as a larger boat. There is still one engine, one set of rigging, one rudder, one set of rudder bearings, one head, one set of batteries, one hull (ok moisture readings take a few seconds, but it doesn't change that much in overall time). Add to this that small boats often have much more cramped quarters, worse access to things.
While I completely get why small boat owners don't get surveys (I don't either) that doesn't mean that the surveyor is going to spend significantly less time surveying a 22' boat versus a 30' versus a 40'. Now as the boats get bigger they may have more systems and greater complexity which could add to the time it takes to do a good job, but that isn't dependent entirely on length.
I spent 12hrs surveying a 45' boat yesterday. If it took me more than 1 1/2hrs (moving very slowly & having a coffee break) to survey a 22 footer with an outboard motor I'd find another way of making a living.
Do you really think it takes as much time to survey ....
a 45' ketch with two masts, , 7 hidden chain plates, miles of hidden electrical wiring, hundreds of electrical connections, two shore power outlets, fourteen keel bolts, 12 throughulls (five of them hidden) generator, inverter, two battery chargers, two galvanic isolators, two isolation transformers, four battery banks, five battery switches,, 11 pieces of navigation electronics, two heads with convoluted waste plumbing, a propane system supplying a stove, catalytic heater and instant water heater, diesel fired furnace, engine driven and water cooled DC refrigeration.
A 22' sailboat with one mast, a single burner alcohol stove, a port-a-potty and an outboard motor ?