Just saw something worth £160 that was advertised of marketplace. Asked to have it. The seller said yes. Then she messaged me to say someone else who contacted her after she'd said yes to me offered her more and could I match it. I said no because I thought that was sneaky and over what I wanted to pay. She then basically unsold it to me and sold it to someone else. Of course she can do what she wants. But AIBU to think that is bad etiquette?