The perceived "money on the table" frequently doesn't exist and attempts to get it may produce the opposite result.
well, yeah, sure, but...
* Who they shift the traffic to may be your competitor.
...at least you know they are paying SOMEBODY, thus supporting the market you want to be in. you can then compete in that market. if everybody who could peer in N places worldwide could just get peering, then all kinds of per-bit revenue for "high tier" network owners would turn into per-port revenue for exchange point operators. where's the market in that? how could a "high tier" even exist in those conditions?
If you assume the above three cases are costs and you add that to the cost of the decreased efficiency of traffic to the target network you can compare it to the probability that you can sell service to the former peer. Depending on the relationship, you can guess the likelyhood.
well, that's a technical consideration, and as such won't matter until we've burned through some of the overcapacity from the dot-bomb era. right now it's possible to do gaming and voip and other isochronous applications via a transit provider who can backhaul your traffic 1500 miles (or 6000 miles) to some centralised peering point and still have reasonable performance. we will need to 1000X the traffic volume again before this stops working again. which should take about a year.