Janet Baraclough.. wrote:

Pure swaps versus paying money, is always a bit of an issue. Some
attendees will be new gardeners or recently moved in, and have nothing
to swap, so it makes sense to decide a fixed price per plant portion or
pot, and to have a cash float for change.

Lots of newbies would take anything, and since they'll hopefully come
back and participate the following years, encourage them. People who
have no plants to offer can bring edible things, a batch of their
favorite brownies, for example. Turn the plant swap into a little
garden party.

Suja