If something has to do with money, it's pecuniary. If your grandfather's antique watch has pecuniary value, it's worth money — you could sell it for cash if you weren't sentimentally attached to keeping it.
Pecuniary might seem like a peculiar word for talking about money, but it all adds up when you learn that it was the worth of the cattle, or pecū in Latin, that gave pecuniary its meaning. In Roman times, livestock served as money in making transactions. Some cultures still have economies based on cattle, but most modern societies have a pecuniary system based on, well, money.