If the vendor is putting in extra time to build something for you, I think it's normal to expect some compensation for it.
Normal salespeople such updates are usually released for free.
In addition, this EA will sooner or later lead to a loss of deposit.
If the EA is going to lead to a loss and you might be right, but on the flop side, why do you care for additional pairs or even bother to use the EA?
Clearly you see some value in this EA and you want to take on the risk. Generally an update or bug fixes in a software should be free of charge, but adding scope to the code base in my view is okay to expect some compensation for it.
Personally I won't be purchasing the new version to get extra pairs, I think the two pairs is good enough and risky enough for me as it is.