Is asking for the same price paid for a new uninstalled RonJon kit fine? Or should I be able to have him lower it since, technically I'm also doing him a favor by buying it off him. To pay the same price I might as well get it from RonJon. And no, I'm not the one selling.

 

IMO there should be a little discount. Not a ton - but a little.

 

I would ask a little less. The reason is simple: why buy from a private party when you can get it for the same price from a vendor. The vendor is 100% reputable and safe, and will definitely provide the support if needed, while the private party simply is not and cannot provide the same level of service.
Now, the only reason one would buy privately at the same price is if the demand is greater than the supply and you cannot get it from the vendor without a wait for resupply.

 

Buying it from the private party you won't have to wait for the kit that is (unless he doesn't have it yet)