Andy: Does anyone have a spare lego ice cream van?
Joe: Bit random?
Andy: I know but it for my sons collection. He is obsessed and he has it in his mind that the only thing completing his collection would be an ice cream van. 
Bob: I have a spare Pizza truck? double Christmas present, unopened. would that do?
Andy: I'm not sure but I'll ask.
Joe: maybe you can put some stickers on and convince him that pizza vans sell ice cream?
Bob: Not a bad idea!
Andy: I'll go for it, how much do you want for it?
Bob: £10?
Andy: perfect! thanks! 
Andy is looking for a lego ice cream van. Bob has a spare Pizza truck. Andy will buy it from Bob for £10.