My Berkey filtration system cost four times that, but is very reliable. The Berkey filters run $50 each, and we run 2 (capacity for four) that is claimed to be good for three thousand gallons. The filters are washable however, and samples tested after washing show great filtration even after three scrub cycles.
If these are legit I will purchase some for the stash...
I have the same setup as you. Three thousand gallons is a believable life expectancy of any fine filter. Anything beyond that I’m leery of believing.