there Is 10 of us total who want to camp but don’t want to pay for an extra campsite since the limit is only 8 people per campsite and it’s important that we stay in the same site can we do that?

If you go during the week you can get away with it, on the weekend you will not.

The thing is we can only afford one spot for two nights.

You're better off just paying what you need to pay for, you will like the place it's worth it.

The ranger comes through regularly, they will evict extra people, having 10 in one site is a lot for your neighbors. Just get two adjoining sites and be cool

You MIGHT get away with it. If the Ranger comes through, which he likely will, you'll have to pay or leave. Not that much money and you get a beautiful place to stay. It's worth the money. Why cheat?