The Ontario parks do not have per person charges unless you are thinking of day use parks only. You pay one camping fee per night and have use of all facilities, trails, beaches, etc. Showers are free and water fill-up and dumping stations are included. Look for radio free campgrounds if you want to stay away from the rowdies.Old Quebec City and Montreal are worth seeing. Ottawa is very nice and has biking trails everywhere. Algonquin park is our gem with moose often seen by the roadside and trails everywhere. Lots of canoeing.
We pay around $45 Canadian/night in a provincial park for a 25' trailer and the fee only includes electrical. We think this is expensive but the lots are usually a good size. People start booking online in February for the summer to get the best spots. The online service rates every site and shows a photo. You can only book 5 months in advance.
You can camp for free on Crown land but you will have no services. Most of these areas are in the north and accessed via gravel lumber roads. See if you can find the areas on the Internet. Caution: if you camp beside a road being actively used by lumber trucks you will be covered in dust (unless it rains) and you have to be very careful driving during the day Monday to Friday as the trucks drive fast and often take your side of the road on a curve.