The only supermarket eggs that I have been able to get are in boxes of 15 in 'mixed sizes'.
That's what it says on the box, anyway, but the last lot weren't 'mixed' sizes, but very definitely all small - they looked so small that I decided, out of curiosity, to weigh each one to check, and they were all around 50g. Yes, I was bored at the time! 
In reality, I'm just glad that I have been able to get eggs at all (couldn't for a few weeks), and want to make it clear that this is an observation, not a moan 