We did not wild camp because there were 8 of us and couple of the group wanted the SAG Wagon option, so 2 guys took turns driving the vehicle with a trailer attached (very long story). Therefore, we needed to stay in campgrounds. The cost ranged from $5 per night to $50 for the group of 8. Many of the sites were honor system, so do what your conscious will allow there, I guess.
Having said that, some of the places we stayed sure seemed like wild camping (lol). Wild camping is going to leave you even more exposed to bugs than a campground/RV site will have. You will want to be able to purify water or have the ability to carry 1-2 gallons with you at all times.
Unlike the US, the towns you will go through are very small and city parks (except in a couple of areas) were non-existent.
If you have access to the internet, you can find a lot of the Milepost info on their website. You will have to print off things or make notes.
Having done the ride, I would suggest you find someone to ride with you - just in case. Cell phone service will be spotty at best. Bears will be prevalent in June. The Black bears won't be much of a bother, but grizzlies can be. In early June, you worry about bears. In late June, as one park ranger told us, you won't worry about the bears because the bugs chased them away. The Ranger was correct. If you have a full body mosquito net, bring it!
It was an awesome ride.