WIBTA if I refuse to pay for a family trip I had zero input on and was told about after everything was already booked?

WIBTA if I refuse to pay for a family trip I had zero input on and was told about after everything was already booked?

So some background: I (26F) have a pretty large extended family and we do a group trip every summer. Usually it’s fine, I enjoy it, no complaints. This year my aunt and two of my cousins decided to organize everything themselves, which normally I’d appreciate except they did the entire thing, dates, destination, accommodation, activities, without asking anyone else in the family for input.

I found out about the trip through a group chat message that said “everything is booked, here are the details, each family unit owes $310, please send by the end of the month.” That was it. No “does this work for you,” no “are these dates okay,” no “is this budget realistic.” Just a total and a deadline.

Here’s the thing. The dates conflict with something I already had planned, a work thing I can’t move. I mentioned this in the chat and was told “we had to pick sometime, you can join us a few days late.” The destination is also a six hour drive which I would have to do alone since I’m the only one coming from my city. And the accomodation they booked is a large shared house which, fine, but I would have liked to know that before agreeing to anything.

Except I never agreed to anything. I was invoiced.

I said I wasn’t sure I could make it work given the dates and asked if there was any flexibility. My aunt said the deposit is non-refundable so everyone needs to pay regardless of whether they come. My mom is now calling me asking me to just pay and “be a team player.” My cousin said I’m being difficult and that this is “just how family trips work.”

I have never in my life been handed a bill for something I didn’t agree to attend. WIBTA if I decline to pay and just sit this one out entirely?