It's a sale

We go out to a fruit and vegetable market early on a Saturday morning sometimes. You can hire a trolley - which we do - by leaving a $10 deposit, of which $7 is refunded when you return it. This morning my partner returned it with instructions to sell it to someone for $8 if she could. This had happened to me once before. By buying someone else's trolley you save a couple of dollars on the deal - and while we've never done it, we have sold ours and made a dollar. And every dollar helps. Alas the whole concept was lost on my partner who was indeed approached by a trolley buyer. How much they asked - and they received the cheery reply "$7". It was only after the transaction was concluded that the penny dropped that I hadn't been making a joke. Ah well. Maybe we'll start on our fortune next time. And to be fair, the first time it happened I had to have it explained to me.