A handmade sign promising cash for diabetic strips

Real repugnance

Should some transactions — even between two willing parties — be forbidden?

The other day, I came across a picture from the US, showing a small sign attached to a tree announcing that someone was willing to buy diabetic test strips for cash. The sign suggests there is unmet demand for such products, and invites people who can meet that demand to do so, thus facilitating a market. But…