Yes, that's exactly what they earn. Two art objects, each of which might be worth a ton if they are lucky.
This happens very infrequently - you have a 5% chance to get an art reward at all, and then only a 1% chance to roll the 2d6*1000 result. That's 1 in 2000 chance, and a typical PC will have about 270 encounters in their entire career from level 1 to 20.
Thereafter, the PCs need to appraise the artwork. Since nobody puts ranks in Appraise and a 12,000gp artwork is going to be very rare and exotic, you have every right in the world to set the DC at "DC 15, 20, or higher." If the PCs fail, they don't know what their art is worth.
If the PCs do learn the item's value, they now need to carry the object across (presumably) vast and dangerous wilderness, just so they can try and find someone who will buy it from them. That sounds like a hilarious campaign in its own right. Can the PCs pawn their Mona Lisa before dragons, international art thieves, and the police find them? Will the merchant they sell to hoodwink them, and what will the PCs do once they find out?