There is a lot more to the issue than just the cost of driving your truck on the roads. If all you want is to drive on and off the lake thru the resort, then I think $10/day is fair enough. But…..normally thats not where it ends. People take their wheelhouses up there and spend several days, and during those days, they will use the shower buildings, throw their trash into the dumpsters on shore, dump their porta-pottys in the septic tank, etc.. The $10/day fee doesn’t cover the expenses the resort owner has for maintaining all those ammenities for the owners of the wheelhouses to use.
IMHO, $10/day for access is fair, but an additional $5-10/day for the “extras” for overnighting isn’t unreasonable to ask for either. Of course, some resorts could tailor those “extras” into a selling point to bring more wheelhouses into their resort and increase their business!