The markup isn't really the issue at all. It's the fact they: keep increasing price without increasing service, fight to keep themselves as the only option so the market continues to tolerate their prices (large difference) as they are the only option and all of this while crying about how much fixing their issues will cost them.
From Wikipedia:
The Standard service tier is Time Warner Cable's base package. At 3.0 Mbit/s download, it was the only speed offered when the Road Runner service was created. It was upgraded to 5.0 Mbit/s in 2004,[8] 7.0 Mbit/s in 2009, 10.0 Mbit/s in 2011,[9] and 15.0 Mbit/s in 2012.[10] The pricing for the Standard service started at $39.99/month, and gradually increased to $57.99/month as of 2014, although promotional and bundle pricing are available.
So if they began charging $39.99 for 3 Mbit/s by 2014 you are receiving 15Mbit/s for $57.99. That means there was a 45% increase in price and a 400% increase in speed. Again what are you talking about?
This is an actual, physical product with a limited supply. Large markups from the cost of ingredients make sense. And this isn't really analogous to ISP's which are essentially pipes which you rent space (bandwidth) to use.
Bullshit. I have a client who was an executive at a major chemical company that produced perfume. The markup is HUGE. Stop talking about things you don't know about.
Not marked up as much as you'd imagine. A significant cost comes from the people engineering the circuits and production methods which you don't see and components can cost a lot as well.
They cover those costs pretty quickly. What they are actually covering are R&D failures which are not related to the successful product.