Ski-Doo is the only snowmobile manufacturer to sell machines that meet the bullshit requirement of Yellowstone's eco-warrior jackasses

In 1997 animal rights organization Fund for Animals filed a lawsuit to ban snow grooming on paved roads in the park. Since snowmobiles were only permitted on groomed roads, the ban would have effectively eliminated snowmobile use as well.

Ultimately, snowmobiles remained, but with new regulations in Yellowstone so that the WINTER ecosystem is less affected (though the summer is wide open for any and every variation of interaction and frequently maxes out the parking and camping areas)

So the national park service only allows four-stroke snowmobile engines. Only Ski-Doo makes them, so far

Ski-Doo’s four-stroke engine, is efficient and emits less pollution than the two-stroke engines offered in other snow machines. The company’s advanced combustion efficiency engines are designed with a square bore and stroke in a spherical combustion chamber and tuned to use less fuel to create power. . 

Of the two Ski-Doo engine configurations allowed at Yellowstone, the 600 ACE is the most fuel efficient with a rating of 28 miles per gallon at 60 horsepower, while the 900 ACE is good for 90 horsepower and gets 21.8 miles per gallon. 

https://www.popsci.com/technology/snowmobiles-yellowstone-ski-doo/

A new Ski-Doo costs around 12,000 dollars on average across their line of machines https://ski-doo.brp.com/us/en/models.html not including the 4-8 thousand dollar kids machines