Royal finances are published every year.
The Royal family, via the Crown estate, are net contributors to the UK economy. It averages out to about £220m a year.
If there were a process enacted to abolish the Monarchy, it is as yet unclear what would happen to the Crown estate. Republicans obviously say it would become state property, others say not. One thing for sure is the Royals would still have a lot of personal wealth and would likely not suffer financially.
The UK economy obviously would suffer, it would need to support a head of state along with their staff. The economy would also, potentially, lose the income from the Crown estate.
So, if one's reasoning for abolishing the Monarchy is financial, it's probably time to re evaluate.
If one's reasoning for abolishing the Monarchy is democratic, why not start a movement for a referendum. Just don't complain if there is one and the result is 52/48 in favour of the monarchy. ????????????