Wedding photogs make a lot of moolah so they should not be skimping on the investment
Not when they start their business they don't, and they don't need as many af points as on the 5d3 which are made for servo af. Actually the 5d3 with the center point af should be quite sufficient for weddings, if it wasn't for the a little higher banding and less very high iso capability.
Wouldn't having built-in wireless eliminate the need for a back-up card slot, though?
... if you have a high end mobile phone or laptop with enough battery power & hd space around to accept the raw files wireless, then maybe - if the firmware allows for an immediate push transmission. But still just a second card should be more convenient.
Other than the 11 AF with 1 cross type I don't see anything that is a disappointment from a lower cost FF DSLR. What did you guys want. A MkIII at $1500?
I cannot imagine it is really just one cross like on the 5d2, much more likely it's just one high sensitivity cross. But to answer your question: Of course no one expects a 5d3 for $1500, but some (including me) expect a firmware- and hardware-crippled body that is designed to protect the 5d3 and is nowhere near the d600.