Why would the prices jump if they can be easily obtained from the FoF events? 73+ are useful for the FoF sets.
I wouldn't say they're "easily" obtained. I mean, the program stamina cost to get them is pretty steep.
EA is known to stick timers on sets like this
^^^ This right here. If there is a good exchange set for 73+. there will probably be a 6 hour or 24 hour cool down, meaning if you stock up 200 73+ FoF players, you won't be able to use them all on this exchange set
Nick slipped up in the stream and started reading the requirements for a "73+ exchange set" that will be used to obtain new currency or whatever it is that will be needed to upgrade the 92 grandmaster's to 94 ovr.
The 73+ haven't been needed for a couple promos so you can currently stash a bunch for around 5k each. I'd expect their AH value to jump once those upgrade sets are released on Halloween.