No scam at all
From their website
Vehicle admission stickers
A vehicle admission sticker is required on all motor vehicles stopping in state park, forest, recreation area and trail parking areas. Buy your sticker when you get to the park or in advance. You can buy an annual sticker, for admission to all state parks and forests for the calendar year, or a daily sticker which is valid for the date of issue.
The 2016 annual stickers are valid through Dec. 31, 2016.
Vehicle admission sticker fees
Annual
Reduced Rate
Annual*
Daily
One-hour**
Vehicle with WI license plates $28 $15.50 $8 $5
Vehicle with WI plates, resident age 65 and older $13 -- $3 --
Vehicle with out-of-state plates $38 $20.50 $11 $5
Bus, Wisconsin license -- -- $11 --
Bus, out-of-state -- -- $15 --
*Reduced rate annual stickers are for additional vehicles registered to the same household address.
**One-hour stickers are not available at all properties.
