The cost of shared ownership is a fraction of the cost of hiring or owning a boat of equivalent quality. In a nutshell:-

It costs roughly £1680 annually per twelfth share to keep a 58-foot narrow boat maintained, and also pay licence fees, mooring fees, insurance, management, winter preventive maintenance, savings etc. (see below for more detail).
That leaves diesel, pump-out and gas (each owner pays for these on a holiday-by-holiday basis) which amounts to an average of about £130 - £150 per week depending how far traveled, etc..
On our standard booking system the owner of a (typical) twelfth share enjoys a minimum three weeks' guaranteed holiday each year (including two weeks in the high season) plus additional weeks subject to availability and at no extra cost.
Each syndicate is free to vary the booking system as desired.
So for three weeks’ guaranteed holiday in a year it costs about £680 per week all-in. If you take a fourth week – usually no problem – it’s only about £550 per week. Much cheaper than hiring!

How are the costs broken down?
Here is an illustration of annual costs for a typical 58-foot narrow boat:
Licence £ 1200
Moorings £ 3000
Insurance £ 400
Engine services&
general repairs £2400
Management £5400
Preventive maintenance £4500
General contingency £1000
Savings £2400
TOTAL £20,300