I haven't read the whole thread, but from what I have read I am actually quite shocked by the number of replies that advocated giving into these bullies - the DCs doing this will only find something else to pick on you DS for, because that's what bullies do - giving in only serves to make them feel they have power over your DS because their taunts make him change his behaviour, so IME it will only serve to make him more of a target.
It would be different as in some of the replies, if your DS himself already felt uncomfortable about your choices as some posters have commented over the clothes they were made to wear at school - he wasn't, this is out & out peer pressure & a good opportunity to teach your DS a valuable life lesson.
As some have said, show him the differences in prices & the money saved & how much more sensible it is to buy brands that he likes, but are cheaper. Then teach him how ridiculously childish & silly these DCs are being & to nit roll over & give into DCs who actually arent beaving heaither kindly, or very intelkegently, so to grow a back bone & tell them to sod right off, pointing out to them that THEY are tge ones being dilly, because they would rather pay more money for less tasty foods & drinks -
because doing that will empower him far more than giving in ever can.
& I speak from the POV of a DC who was taught that self same lesson myself & it has stood me in good stead in life. So long as I know I am doing the right thing, I never actually give a flying one for anyone else's opinion, I am so glad my DPs & more so my very feisty DGM took that stance as its made me who I am today - the bully's soon backed off when they realised I actually didn't care, so their taunts were like water off a ducks back, if anything the taunts made me look down my nose at them for how silly & ill informed they were.
I also speak from the POV of the parent whose DD had similar taunts, though in her case it was because her packed lunches were too healthy - in a healthy eating school FFS
- there will always be something that bullies will pick on, that's just life - the trick is not to be the victim & allow it to bother you - DD laughing back at them for not liking the things she liked & thinking she would care about their opinions on what SHE chose to eat, which also just so happened to be good for her.
Your DSs response should be - yeah, Aldis stuff is great isn't it, I actually like the taste better than - insert brand they have - & my DM is so clever as it saves so much money, which means she can treat me more for Xmas & birthdays - oh what a shame your DPs don't do that.
& yes, if it carries on, do flag it with the teachers, because it is bullying & needs to be watched as it can escalate further - standing up to bullies & laughing it off will have them lose interest & grow some respect for your DS far quicker
Good luck