So personally I've always adored Christmas Parties. I was sad when we didn't have one in 20/21 because of COVID-19 and sooo many people had kids during these years.
But if you host a free Christmas party outside of work hours and people attend, it may just mean you don't suck. Transversely if no one attends, us this as an opportunity to improve. Also, don't make people pay for shit, gtfo of here with that nonsense!
I've attended both paid and unpaid events. Unpaid were always optional but they had high attendance. Granted, they usually include good food and alcohol with the inclusion of a SO too. The paid parties were when I worked in Retail at Verizon. We held them during a shift where either everyone or almost everyone was present. Cannot confirm if alcohol was present or not though