Why?
A subscription to Netflix already grants me access to way more than I can reasonably watch. If my tastes were perfectly aligned with what Netflix offers (or Disney, or Amazon Prime, et cetera), I could live this exact scenario of everything I could want for less than $10 a month (and some people do).
But if my interests are even slightly more eclectic, I get to pay for each service separately, which is silly if we assume that the production costs are equal for the sake of argument. And even then I would miss out on lots of content because it is being kept in a vault until copyright expires, or because it is geoblocked because the content owner is fishing for exclusive deals, or some-such nonsense.
So economically, $10 a month seems perfectly feasible.
Also, keep in mind that the outrageous costs of the US traditional cable package are very US-specific. In many countries cable television never got that expensive and broad. For those consumers the notion of paying more than $30 a month just for television (no internet included) is absurd.