Full Site for all of 2018: $44,458
I would have to agree with Bama Ed on this.

His figures are right on.
I went and looked at the Disney site for available sites for every month in the full hook-up category, since that is what we stay in:
January: entire months stay is sold out, all sites, one might be able to piece ressies together.
February: all site category's are available, full sites avg. 103.67 per night, total cost, 3,148.94
March: all site category's available, full sites avg. 146.07 per night, total cost, 4,929.75
April: all site category's available, full sites avg. 120.28 per night, total cost, 3,924.08
May: all site category's available, full sites avg. 111.50 per night, total cost, 3,763.23
June: all site category's available, full sites avg. 111.17 per night, total cost, 3,627.10
July: all site category's available, full sites avg. 115.10 per night, total cost, 3,884.71
Aug: all site category's available, full sites avg. 93.43 per night, total cost, 3,153.43
Sept: all site category's available, full sites avg.
86.83 per night, total cost, 2,832.79
Oct: all site category's available, full sites avg. 93.00 per night, total cost, 3,138.75
Nov: all site category's available, full sites avg. 96.17 per night, total cost, 3,137.66
Dec: not available for entire month as it is still 499 days out, would only be able to look until Dec. 3.
Total cost for beginning of February to end of November: 35,540.44 with tax.