This is way too old-skool to have much relavance here, but I can make you a set of coustum shoes for your saddle-horse for about $20.00 ,,,,, but if you wanted a set of shoes for your draft-horse, I would need closer to about $45.00.
But the real cost difference is the pure fact of numbers, distribution and retail cost.
Say a dealers cost is (just a guess) is $800 for that 660 , but $1300 to stock that 880,,,,, money, even if it's sitting on a shelf has a value.
The same with the distributor, he needs a cut,,,,,,,, but just think of the huge cost deferents there is deprecating the tooling to make them,,,,, if your set up to make 1,000,000 somethings, that will sell fast, compared with setting up to make 1,000 somethings that sell slow?