Whatever your estimate is, double it. The misc. catagory covers many things that add up in a big way.
Without splurging too much on full featured CGs, without going to restaurants every week, without driving hundreds of miles on average but without skimping on anything we figure $100-$125 per day for running costs.
Then there are the fixed annual costs like storage, insurance, at least $3000 for maintenance. You don't want to hear about depreciation.
Only use it for a few weeekends a year & the per day/use costs really escallate.