The tiers are only necessary bc the establishment players act as gatekeepers and try to charge excessive fees for electronic access. That other tiers exist shows how much ingenuity exists in the rest of the industry. 20 years ago anyone would have laughed if someone had described the tiered structure of ETNs. In my opinion it's an amazing triumph.

Incidentally, the NBBO rules are sold as a way of protecting the interest of the little guy, but they simply concentrate power with the big exchanges. Obviously if you're trading on a peripheral ETN and getting free transactions you are OK with being a few cents off here and there (and if you're too dumb to realize you're overpaying for something, your strategy is not likely to succeed). NBBO imposes a huge network tax on the entire system, which is deplorable.

In a properly decentralized and competitive system, anyone who cares what the NBBO price is willing to pay extra for the information, and those who don't care can take whatever amount of risk they are comfortable with.