How much is a tradable copy of Rift Storm Legion worth?

It's not available from the store anymore... but it sold for $39.99 when it was. Sale price went as low as $23.99.

The game is Free to Play right now so the max it is worth is $15 for a one month sub, which is what it came with. Honestly I think it no longer has even that much value because it has been given away by Trion Worlds themselves so much and was given away on Raptr (all non Steam, but I think you get the point.

have to do some research on the trion worlds site, but owning that expansion gives you some premium perks
I believe, like extra bag space/slots, maybe an extra character slot or something, sorry I cant search for it now,
but i think you get stuff like that.