Disclaimer: I'm a dairy goat person who "dabbles" in cows, having a pet/beloved Guernsey family milk cow for the past 7 or so years & just recently adding Jerseys - little-ish ones, but not those waist-high ones that cost a couple of appendages just b/c they're cute & small, & trendy. (there are a couple of mini breeders who are also breeding for nice udders & good production, on milk-test & everything, but sorry, the majority are breeding novelty pasture decoration type things to make $$$)
I don't know abt asking the breeders of the $$$ Minis - of COURSE they'll tell you how fabulous they are & how your life isn't complete without one, LOL!
I wholeheartedly agree w/ the people who are talking about efficiency. I don't see any sense in feeding something that eats as much as 8 goats, & gives as much milk as 1 good goat, either. It's a farmer thing. We can't help it.
Matter o' fact, I bought one of those a couple of months ago in the form of a smaller-statured Jersey (46" at the hip). I bought her w/ an even smaller-statured Jersey (43" at the hip so qualifies as a Mid-Sized Mini) who gives 3.5 gallons (both first fresheners, BTW), is as sweet as can be, & doesn't require a bunch of fancy feedstuffs to keep giving pretty close to that much milk, even being accustomed to the silage/grain/etc. commercial dairy diet & transitioning over to my minimal grain/grass-based regimen.
I got a really good deal on them b/c the kid was wanting to go "Show Holstein" with his herd & had his eye on some $$$ stock, so wanted them outa there & the $ in there ASAP, to go buy his fancy show heifer, LOL. He also fell in love w/ our Farmcollie puppies & suggested deducting her price from their purchase price
I sold the bigger/low production one just a couple of weeks after their purchase b/c she was one of those "stereotypical temperamental Jerseys" you always hear about. Plus, I really do NOT see any sense in feeding something that big, that much, only to get a gallon & a half of milk. That's some expensive pig feed! (their primary job right now is finishing out pigs, LOL)
I also agree w/ whomever said to just make your own - find a nice, smaller statured Jersey, if possible - if not, just a **nice** Jersey since that's most important - & breed her to smaller-statured bulls!
I'm a research junkie & keep a close eye on "the market" to be sure the price is fair for what I'm buying or selling, & Jersey milk cows are running anywhere from $1000 up to double that, just depending on if they're in milk, bred back, how much they're producing, how "family milk cow-ish" they are, pregnancy tested, location, stuff like that. All of those criteria hold monetary value & factor into price.
& oh yeah, be careful b/c they're pretty addictive! After selling that persnickety low-producing milker, I bought a group of heifers that I didn't need - but boy were they cute & awwww, in need of TLC (& I'm a sucker, LOL) & . . . yeah. It's hard not to succumb!