I've eaten Muscovy and love it.

Muscovies being so extremely well insulated, they take a
lot of plucking.

I can see why anyone would charge a lot to prep the whole carcase. He was naughty to quote one price then put it up - maybe he hadn't realised they were Muscovies? Or perhaps hadn't prepped a Muscovy before? He still should have done the first batch as per his quote, though.
The legs and wings are tasty, yes, but even though there's more meat on a Muscovy than a Mallard-sized duck, I found it took a bit of cooking - long and slow - to soften up the tendons and make it other than tough and stringy. I wouldn't cook and serve them alongside roasted breast, they wouldn't get enough cooking.
The concern I'd have about 'breast only' is does it mean no skin? The crackly skin is part of the joy of eating duck breast, to me - and certainly confers a lot of the flavour. If they are removing the skin to reduce the amount of work then I'd think you'd cook it sliced in stir fries or cubed in sauce, rather than as straight 'duck breast'.
Also of course you'll always get better flavour and texture if you can cook on the bone.
I wonder if anyone could do a proper 'crown' of Muscovy? Ie, all the breast, breast skin and breast bone, removing the legs and wings and back end bones. They'd only have to pluck the breast (ather than the entire carcase) but you'd still have all the flavoursome bone and skin around the breast.
I'd have thought it would be possible, and with a Muscovy drake, worth it, to skin the legs. They'd still be very tasty and have quite a bit of meat casseroled.