There are three pricing shapes in this market and they're worth separating before you compare quotes. Flat subscription software charges you a monthly fee, sometimes scaled by site count, and the booking is yours. Transaction-priced platforms charge a percentage or per-reservation fee, and several of them let you pass that to the guest as a booking fee at checkout, so your quoted "percentage" may or may not be an expense you actually eat. Legacy desktop software like Campground Master is sold as a license with optional support, which is genuinely cheaper in cash terms and gives you no online booking engine unless you bolt one on. Pricing moves, so get current numbers in writing from each vendor for your exact site count rather than trusting a range you read anywhere, including here.
Separately from software, budget card processing at roughly 2.5% to 3% plus a per-transaction fee. That applies to every dollar regardless of which system you pick.
On the listing sites, they're a mix. Some are directories where you pay for a listing or an enhanced placement. Some are true booking channels that take a commission on the reservation they send you. Ask each one which model applies and whether the commission is on the site fee only or on the total including taxes.
The part that surprises new owners more than the software bill is cancellation policy. Online booking floods you with reservations made four months out by people whose plans change, and a soft policy on a 28 site park in peak season is a bigger annual number than any subscription. Decide the policy, put it on the confirmation email, and enforce it.