I think it's the gas limit that matters if you "get in" or not, the price or Gwei is just how fast you "get in" But seems he entered Gwei wrong 21000 instead of the normal 21 is insane! I had 21 Gwei and 300000 gas limit and "got in" with a total fee of 0.00598 Ether ($1,71). So I used about 290k gas and that guy had gas limit of 260k and ran out. Please feel free to correct me if this is wrong, just my own thinking.