Comparing a conventional sloop to a boat with a freestanding rig there is more cost in the mast - but no rigging to pay for or maintain and a much smaller sail inventory as well.
There are always few willing to build a boat very different from the norm. But there have been many over the years, some quite successful such as Rodger Martin's "Grey Wolf" shown below. Tanton has also designed many boats with free standing rigs - his most popular is the Tanton 43 - 2nd pic below.
Living aboard in Victoria Harbour