I was in that exact situation and I ended up having to drop that group of friends because I couldn’t afford the extra costs for everyone else, every time we went away for the weekend.
As our costs were mainly for accommodation , the price went up by far more than eg £10 each time, as the extra amount was divided between fewer people each time another person cancelled. Also the closer we got to the event , the more inventive people were with reasons.
So Annie dropped out 5 months before because she decided she wanted to save for another holiday so it was just £20 extra each ( Annie’s cost of £200 divided between 10 of us ).
But then when Bob dropped out 6 weeks in advance ( because he couldn’t get the time off work ) 9 of us had to share that £200. So that’s £22 for him and 20 for Annie = £ 42 each.
Then the day before , Claire said her child was sick , the cost was her £200 for accommodation plus £60 for food and drink already bought = £260 / 8 of us which was £32. In top of the £42 extra we had paid for Annie and Bob.
So the weekend that was going to cost us £260 each ( 200 accommodation, 60 food and drink ) became 260 + 20 ( Annie ) + 22 ( Bob ) + 32 ( Claire ) = £334. That’s nearly 30% more.
Several people complained when Claire expected everyone to pay her share, but she said that we let Annie pull out for a trivial reason and no one complained about Bob but her reason was more serious and she “ couldn’t help her child being sick”.
And before you ask, the child only had a tummy bug and yes they had another parent. No Claire was not struggling by on benefits while the rest of us were millionaires. And no the weekend was not to Outer Mongolia so if the child had developed Lassa Fever over the weekend, Claire could have driven home in 2 hours. And no she wasn’t autistic and no , we were not all jealous because Claire was prettier than us . ( I think that’s covered all the usual Whataboutery ).