Closer to cities where demand is higher, the campsites are more desirable and therefore the ghost booking issue is worse. A higher fee discourages that. On the downside, you pay more for convenience of not having to drive far.

The tier system described appears to be more based on available facilities though rather than visitor numbers, while it does mention demand in passing this isn’t quantified and the tier table shown works off facilities/servicing.

I would agree there does tend to be correlation between high demand campgrounds and highly serviced ones so you do have a point with high prices being necessary to some extent. I do think though that applying a state wide pricing system will end up with noticeably higher prices in a lot of places not near the major centres (or the major attractions).