Evening all 
I'm a newbie and this is my first post. No worries if you're too shattered/busy to answer this or if you just find it a bit pathetic that I even cared about this wee "injustice" but I was just curious to know if it had happened to anyone else?
I'm a besotted Auntie and part-time sale hound. Recently I hit the M&S sale - v. chuffed to find a 3 piece Minions swim set age 5-6 reduced from £20 to £6. Then in another branch I nabbed the exact same set age 3-4 only this time it was priced at £12.
I queried this with the lovely lady on the till and she looked it up online, where it was sold out, with sale prices running from £6-12 (age range starting at 3-4).
Now I'm well aware that one of the sucky things about shopping for little'uns is that the shops increase the prices for larger sizes 
. However, in this case, M&S priced the smaller set at double the price of the bigger set.
And this is the point where I have to apologise to anyone who was standing in the queue behind me. Because this is when the lady at the till called her manager over for a second opinion and I'm pretty sure I heard the folks behind me dying inside as I became 'that girl'. The one who, while friendly and polite, nevertheless made an uncomfortably long queue even longer. 
Turns out the Till Manager wouldn't honour the cheaper price, explaining that sometimes different factory batches are priced differently!!?? She said that although the sets were identical, the 3-4 set could have been from a more recently produced factory batch and would therefore be more expensive (an argument that I could totally understand, if we were talking about fresh milk and not a rash vest!? 
That said, she may have a point about factory batches, given that both sets have different label codes BUT:
- they remain identical in everything but size (and label)
- when u search the M&S site using both label codes, they each redirect to the same page (link at bottom).
Anyhoo, I queried this with M&S customer service (something i rarely do but on this occasion I just couldn't help myself
And wouldn't you know but they emailed back with this incredibly helpful explanation 
:
"I have had a look at the items and on the system I can see that certain sizes are marked down to less than other sizes, the 3-4 has only been marked down to £12 so that is the correct price, whereas the 5-6 has been marked down to £6. I hope this helps"
So, for anyone still reading this who hasn't nodded off in the middle, HAS THIS HAPPENED TO YOU BEFORE? I mean, IS THIS A THING? Do the shops not only raise prices as ages go up but also raise prices for smaller sizes simply because, presumably, they're more popular in that size (ie. 3-4 = minion fan / 5-6 = spiderman's sidekick) ?!
Over and out - (here endeth the mini rant 
)
ps - wouldn't you know but as of just now the set is no longer sold out online so if u click on the link below, you can find size 6-7 priced at £7 and size 3-4 at £12
bit.ly/2y5c5Mx
ps - the sequel - On second thought, maybe they're just slashing prices for the sizes which have the lowest remaining stock levels? I've seen that before for kiddie clothes, but it always seemed to be the smaller sizes that were slashed. Hmm, I'm wondering if i've just answered my own question. Not that I like the answer but...
ps again - it's now a trilogy - at the very least, i hope this post either made you chuckle or was so tedious you finally got some much needed sleep!