6 year old machine with just 50-100 miles is rare, but that won't do much for the price. I'd say, take what you bought it for back in 2017 and reduce that by, oh, maybe 30% and see what kind of action you get.
Every area is different in snowmobile prices. Best to look at your local craigslist, facebook marketplace and for sale ads locally and go from there. At best maybe take it to a dealership to ask them what a used snowmobile like that would go for. Some dealerships are willing to give you an estimate for a private sale or auction if asked nicely or if you buy them lunch or beer for the fridge in back.
And as always, spring time is the worst time to sell a snowmobile. Prices have to significantly be less because most folks are looking at ATVs and bikes and such to spend their money on. If you can wait, best time to sell is just as the season starts, especially if it's a good snow year.
Check local listings, call a dealer and do what I said. That is your best bet especially during the summer. As dan said you are better off waiting till fall/early winter say Nov or so before selling otherwise you won't get close to what it is worth.
I would look at the shock package and any extras before I would consider $10 for a 5 year old sled . I paid a little over $11 for a new 2019 Polaris 600 XC 129 including a cover, belt and gallon of oil.