Well, that's not fair.
They aren't charging you for an extra 8GB module, they are replacing your 8GB module with a 16GB module. What's the price difference between a single 8GB stick and a single 16GB stick?
They aren't charging you for an extra 8GB module, they are replacing your 8GB module with a 16GB module. What's the price difference between a single 8GB stick and a single 16GB stick?
edit: But looking at the hardware pics it looks like it is single module but more than that, it looks like the RAM chips are soldered directly to the motherboard. Not a RAM module soldered to the board but the actual chips which means the cost to apple would be even less since you just double the ICs.