What other transit ISP gives you a discount because the traffic is local?
Do you or your customer get a discount when you're both only connected with a transit ISP? No, both parties pay for connection to the transit ISP (even if it's the same).
Traditional wired telephone networks are almost always caller pays (although cellphones in the US are caller pays toll, callee pays for wireless segment), but IP networking has always been both end points pay. It's not some new thing Comcast (or whoever) invented in 2006 or whenever.
If you want to connect to customers behind ISP A, you typically need to pay an ISP that's connected to ISP A, or pay ISP A, or qualify for peering with ISP A. If you and ISP A are both paying ISP B for that data, then there's motivation for you an ISP A to peer; if not, ISP A says we're happy to take your traffic through peering with these ISPs or you can pay us for a direct connection. Maybe a bit less cost for 'paid peering' vs a full transit connection.
In the old days of dial-up, all you needed to start an ISP was two T1s, one for your uplink, one for your modem pool. Once you got a little bigger, you'd look to see what content networks you could peer with to reduce your transit budget. After the move to broadband which has a bias towards only two, maybe three companies running wires to homes, and the FCCs abandonment of mandatory line sharing from the telecom act of 1996, we run into the situation where there's a handful of residential ISPs nationwide, and they almost all run transit networks, and there's no longer an economic incentive for them to peer with content networks --- they can justify peering with most other transit ISPs, so there's no cost savings from peering; and they have no competitive need to offer better service.
The solution isn't mandating 'neutral treatment', it's mandating competitive local access markets via mandatory line sharing[1], and splitting up the national transit business from the last-mile business, ala 1984 AT&T.
[1] But with tighter regulations, so that incumbents can't cross-subsidize retail prices to be lower than wholesale pricing as was common in the early 2000s before mandatory line sharing ended; building out new wiring where line sharing was infeasible was another common loophole. It'd be way more competitive if the wiring providers weren't permitted to offer retail services, but that might be a bit too meddlesome.