Your getting away from the point of what you responded to. The previous poster to whom you replied was explaining the costs of having to buy double of everything. You stated that you had all these costs with 2 under 2. I explained the difference for you, around how you would benefit from staggered costs (I.e one in a highchair one in q booster seat, ones nursery funding ending when the others is just starting that list is non- exhaustive BTW. As you have no answer your essentially handwaving this away as "being irrelevant" when we have tried to educate you on the impact of paying double every time upfront.
You clearly do not want, or wish to understand the financial impact of twins. I would consider you wholly unsuitable to be the person who knows of others contributions as you appear to have neither the sensitivity or tact to manage such a situation, best you do everyone a favour, and bow out?
I had two in different classes, I would put in twice but I could not afford much anyway, as I'd worked in a school years back I always quietly valued the handmade cards or small gifts the parents had supported their children to make. A collection would have felt more like a thank you from the parents, which whilst is also fine. However my kids had no idea when on one occassion I did contribute to the class collection what had been bought and no one told me until I asked. I didn't contribute the following year when the organiser informed us of her fee to do so.
People contribute what they can afford, it is not mandatory.
I also knew a mother of triplets As I goy to know her better it was clear she had a controlling abusive husband, can you even begin to appreciate how stressful, and potentially discriminatory to her children your judgemental views would be. I would also be concerned around your potential lack of discretion.
I always bought two gifts if both were invited so each had there own to give. They are two different children, however it was still less per head money was tight.