Of course we should minimize standards when possible. Things you can do with dropping vs. queueing are quite different, but not useful to mix, because end-nodes can't count on behavior in that case. We think that sending extra traffic and dropping in the net adds extra load and complexity. Better to mandate never sending over traffic agreement for premium service. Heard a number of schemes that replace best effort with something else that is not a hard guarantee.
Pricing is based on service during times of congestion.