As a seller, I usually give the person 24-48 hours to respond back with payment before I deliver the item/krono, even if another person is interested in the item and are offering more, just out of common courtesy to them since they were interested first. I even tell the other interested party, that someone else was interested in the item first, and if I don't hear from them in 24-48 hours then I'll PM them back regarding the item/trade. If I don't hear back from the first party in 24 hours, I usually PM the initial party too, usually multiple PM attempts to contact them, before contacting the other interested party as well.
Of course this is just my policy on it. Every seller has their own way of handling it.