On the one hand, the rabbits look healthy enough (you'd have to get your hands on them to ascertain that) and seem friendly, and the set-up looks pretty clean. $580 is a decent deal, although you'll probably have to invest in some trays or some other arrangement to divert waste if it only comes with the two trays pictured - the top rabbits will be dropping waste onto the bottom ones. The nest boxes in the photo have seen better days, but you could probably hammer them back into shape and replace the bottoms.
I would be a tiny bit leery if you really want high-quality pedigreed silver fox; whether or not these are a good deal really depends on what your purpose in breeding these rabbits is. I cannot even guess from the photos what the quality is. But at least these look like well-cared for rabbits.
Having learned from experience, I'd insist on examining each rabbit, to get an idea of temperament, as well as to check teeth (worth doing, especially on the juniors!), vents, and get a feel for the overall health and type of the rabbits. If you are inexperienced at handling large rabbits, have the seller pull each rabbit out and show you teeth and vents, and pose the rabbits on a table to let you run your hands over them. You should not be able to feel the spine or ribs. If the seller doesn't want you to handle them or to show them to you, that would definitely give me pause.
If you want to breed silver fox, my suggestion is to go look at them, but go with the firm intention of only buying them if they are what you are looking for. Be prepared to go home empty-handed if they are not (if the rabbits look unhealthy, underweight, aggressive, etc.). Cages etc can be fixed/changed, but that's a lot of little lives to be responsible for if it's not a good fit. And have a plan for dealing with them, if it turns out that's too many rabbits to handle when you're just starting out.
A side note on nest box warmers - rabbits shouldn't need those if they're good mothers. Our does routinely have and care for kits at temps well below freezing. A nest box warmer just tends to make our rabbits want to sit in the nest box, which isn't a good thing for several reasons.
