It does sound like a lot of money to invest, and all the more reason to push drivers to get personals. I know of one club that is now chargeing the drivers a deposit/rental for the use of club transponders, not such a silly idea.
The original batteries in the AMBrc transponders dont seem to like living over the 2 year mark, and our club bought our set just before they changed their warranty from 2yrs to 3yrs.

Jeff is very good with his service, another happy club.