This is totally false. Inter-AS traffic is often priced using bandwidth in peered connections. In a bandwidth discrepency situation one isp will usually have to pay a lot more for the inter-AS traffic.
Right, and that's the sender, which is what I said. Note that the amount of traffic is effectively irrelevant since the connection is supposed to be dedicated. The only reason why the amount of traffic matters is that you need to decide which side pays what.
No. Generally the agreement works like this: "we'll set up a peering agreement between us. As long as the traffic differential is within 3%, peering is free. Beyond that point, the exceeding party will pay an excess penalty of x/GB."