They're not on sale, they're from the outlet. I'd prefer to buy new. I just haven't decided whether getting a sub in an apartment is a good idea or else I would have one already. If you do see new subs on sale, please let me know though.
If you are measuring out of circuit (so there is no confusion with any other parts on the board) then they are dead. Gate to drain or source is diode-like. Depending on the JFET, drain to source will be tens to hundreds of ohms either way around with the gate open.
Possibly a turn-on transient while the tube warms up has killed them? Without seeing the schematic it is kind of difficult to tell for sure.