I don't sell anything on Ebay so I would know for sure, but do they have to set items up separately for mobile view etc? I ask as I bought some screen protectors for my phone a little while ago and when I looked via my phone app they were £1.85 for 5 with free delivery. I bought them but as soon as I had the postage went up to £5? I was just about to message them and let rip when I noticed that continuing to the next stop the postage went back to being free. I can only assume then that cross platform Ebay can screw up how it displays.