Part of that cost comes from ATT and Comcast using their government sugar daddy to make running fiber as expensive and difficult as possible.
Example: https://arstechnica.com/tech-policy/2018/01/att-and-comcast-...
Though - my personal opinion is that old copper that no one really wants to maintain is wasted space for cabling that could support significantly higher bandwidth at lower latency. Telcos are already refusing to replace destroyed landlines and instead substituing LTE service or otherwise instead for a decade now.
You're assuming the only place price reductions can come from is lower profits and there is no room to e.g. reduce waste or increase efficiency, which monopoly providers have a long tradition of not even attempting to do. Which usually means there is a lot of low-hanging fruit there.
Their subsidies and ability to charge different rates is partially based on their accounting. So they play Hollywood accounting tricks (https://en.m.wikipedia.org/wiki/Hollywood_accounting).
They have been chastised on this repeatedly. For instance, "The FCC Had To Remind ISPs Not To Spend Taxpayer Subsidies On Booze, Trips To Disney World" (https://www.techdirt.com/articles/20151022/09232532594/fcc-h...) here, the $1,300,000 spent by an executive to buy a house for their children's use as college housing wasn't part of the profit. That's simply the cost of running business, as essential as keeping the lights on ... nothing wrong with the twice a week $96,000/year massages either, I'm sure that's got a lot to do with FTTH residential deployment. Oh wait, the taxpayers built that.
This has happened a few times, such as with verizon (https://www.huffpost.com/entry/are-the-salaries-of-veriz_b_9...) where the 4 top executive pay (without benefits) was $41 million ... which would have been fine if it was in their operating expense and they could afford it.
But they did this because it wasn't and they couldn't.
If the telcos make something called "Local Service" unprofitable when compared with "Corporate Operations Expense" (which includes jets, multiple homes, multi-million executive pay, etc) and technically run "at a loss" they can legally raise prices and reduce service.
Because they can make things look unprofitable, federal regulation permits them to raise prices to make up for it. It's an perverse incentive, an executive spends $100,000 a year on pet care to make sure local service becomes unprofitable and then they can use a legal procedure to raise prices. rinse, wash, and repeat.
So yes, it could be 1/4th the price but no, the free market is the most efficient allocator of goods, we're told. They do things the cheapest we're told, there is no alternative ... yeah, bullshit.
High speed internet is $7.67/month in Russia, $5.41 in Ukraine, $6.12 in Venezuela and $63.07 in the USA. Ah, the magic of trusting the market. Can you feel it!?
Also the poster you replied to specifically said ADSL1 which has been superceded more than a decade ago by ADSL2, ADSL2+ and VDSL. These aren't fibre technologies and in most countries are sold at the same price.