It's a voluntary contribution not mandatory, they don't even need to give £10 if you don't want to. One of my children's classes we do it as a voluntary contribution of up to £10 or whatever people can afford, there's no pressure to contribute, plenty of people do their own thing or do nothing. The card is signed from the entire class no matter who did or didn't contribute, no one is singled out.
My other child's class the woman who always organises it, does it through her work, she gets commission on what she buys. I don't think she contributes herself (she has 4 children in the school and is a single mum, she volunteers for every class collection, christmas, end of year, people sick, people leaving etc). She decided the contribution was to be doubled for each to £20 (not contribute how much you can afford), now there is no way this woman was putting in £80 twice a year for class presents she was clearly contributing £0 and taking the commission and even a bit of the money for herself, there was 0 transparency on what she bought and where the money went. This led to half the class to bow out of class collections. The card is always signed from the list of names who contributed too, not the class. No one should be told how much they NEED to contribute, it's a token gift, teachers really don't want some shit someone else chose. I know from teacher friends the gifts appreciated the most is a hand made card from the child/card from the parent, just saying thank you and 1 friend loved it when the class collection got her an amazon gift card, she got to spend it on something she actually wanted, she didn't expect it though.
This parent can give £10 or £0, just because someone appears to have a good job and be well off doesn't mean they don't have a massive mortgage, car payments etc etc, you don't know anything about anyone else's finances, besides even if they are well off it doesn't mean they want to or have to contribute.