I am also turning 40 this year and spending on a big party. I have also asked for money as I want to buy myself a ring after my birthday , as something that is timeless and I can pass down to my daughter, and actually avoid getting lots of gifts and people in my eyes spending more money. We did money for our wedding for the same reason and it was pooled together to buy our kitchen table.
I have done money for my birthday , which is being co-ordinated by a friend, so I don’t see what people are gifting individually as I don’t want them to feel any pressure of how much they gift. The party and event isn’t about the gifts, so if someone wants to gift £10 to the pot they can. I know people won’t come without a gift so pooling money, means they don’t need to try and think about something to get me, and risk an unwanted gift as I am not materialistic , live a minimal life and not anything I want, I get asked every Christmas what do I want and even my husband struggles.
so for me I would not get worrried about what they are spending on the party, that is the choice of the birthday person , and I for one do not expect the ask of money for a present to be reflective of the party cost. I have invited people to come and join me to make my birthday special and get all my friends and family together.
I agree £100 for a friend is a lot. I wouldn’t expect that. My family on average gave £40/£50 . So for friends I would expect less, and happy with £10. The gift is not the focus it’s the party to bring people together, people shouldn’t feel a pressure. And my party isn’t a cheap occasion , we are spending around £5k with catering, band, marquee and alcohol.