I don't think you understand how pricing works. Someone like Disney demands a high carriage fee agreement and mandates that ESPN must be in the basic cable package for all comcast subscribers, otherwise comcast doesn't get any Disney owned TV. As a result Comcast has to charge basically 10 bucks a month to all subscribers to have ESPN, not counting the general cost breakout for other disney owned channels. Sure, comcast leases STB's for X dollars and gets a cut of the subscription fees as well, but the point is the people that make the TV programming are the same. So it's not magically going to make the cost of TV significantly cheaper by cutting out comcast. Comcast is the person that collects the bills, but Disney, ViacomCBS, etc, are very much involved of setting up the prices consumers pay on cable and streaming.
Edit: Also add in the risk and churn factor. With cable bundling, TV programmers had scale and predictability on their side. Basically all cable subscribers had long term subscriptions and could guarantee a high volume of subscribers to collect from. With DTC (Direct to Consumer) streaming apps, consumers can churn and temporarily subscribe for monthly intervals. That means you have less subscribers at any one time on your app and for shorter durations. Guess what that does to the revenue. So if you no longer have the economics of scale in terms of long term subscription length and volume of subscribers, the cost for individual subscribers will probably have to keep creeping up and get possibly more expensive than cable.