I have a pair of 2A3's - which i had as spares for an amp i sold earlier this year. My current amps use 6B4G's, and i cannot see me changing in a hurry, so the 2A3's are surplus. I probably used them for a max of 50 hrs, and i think they had similar usage when i got them ( so 90-100hrs max). Not sure if they are a matched pair ( cannot remember) but both have the same plate current measurement of 56ma.
Accounting for my usage i think £25 +pp is a fair price.