I understand your assertion, and simply disagree with it profusely.
There was no "understanding" associated with the tax-relief. If there was, it'd be codified in the laws and regulations surrounding such tax relief. If there had been such codification, this wouldn't even be a discussion, it'd be "no, your statutorily prohibited from doing that," or "OK, that's fine, but to do it, you need to repay the $nnn,nnn,nnn,nnn.00 in tax relief that was predicated on not doing so." Instead, folks like yourself - who actually don't understand the issue at all, get all hand-wavy about "we gave them tax relief" and assume that there was some actual agreements codified around it, which weren't actually there.
Let me be clear on something: you haven't paid for "a packet". You've paid for a pipe, capable of a given flow-rate. In this case, Netflix (for example) has also paid for "a pipe", capable of a given flow rate, into the system you get your data from. It's not nearly big enough, though, to service all the people who want to consume data from Netflix. Now, your argument is that the people who sell the pipes should just give Netflix a bigger pipe and take it on the chin because goddamnit you want to watch your Breaking Bad reruns. But the pipe Netflix needs, to do what you're asking, is really goddamned big. Big enough that if Netflix wants a pipe that big, it should damned well pay for upgrading it themselves. That includes both just the physical pipe, but also whatever the people who sell the pipes need to charge in order to able to handle the inflow of data from a pipe that big, sending it on to all the various places where those bits are going to drop back out into your laptop.
Your attempt to fixate on "charging for packets" is laudable. It certainly makes for a more compelling argument, or it would if there were any companies charging "by the packet" instead of "by the width of the pipe."
By all means, though, if you want to go to "paying by the packet" billing, I suspect the telcos and cable companies would be happy to oblige. It's a much more tenable business model for everyone involved, charging metered service, so that those who put the most actual strain on the network pay the most. But the last time a carrier tried that (TWC, 2008, in field trials in Texas) there was a hue and cry from folks - on this very site - against such "paying by the packet".
So, believe me, I very much understand the issue, and have been paying attention to it before you had even heard the phrase "net neutrality."