The problem is the same as it is with print; the subscription fee usually only covers the cost of distribution. The cost of content is typically paid for by advertising, which brings in more than subscriptions do. This CBS streaming service is going to be $6/month. So for each million subscribers they get $6m/mo.
But CBS's most show, The Big Bang Theory, which is the most popular show in the USA in that time slot, pulls in about $6.5 million of ad revenue every episode. So CBS would need 4 million subscribers just to match the revenue stream from that one show. Put another way, they need 50k subscribers to replace the ad revenue from one single 30-second commercial spot on that same show. http://www.ibtimes.com/economics-prime-time-how-much-does-it...
This is why the economics of TV are so brutal and many shows are canceled after only a few episodes or a single season. It's not necessarily the fault of the show itself - if a new show goes up against a much stronger offering from another channel, it may not attract a critical mass of viewers and it's more economical to cancel further production and fill the time slot with repeats of more popular material that draws a reliable audience.
Now it could be possible for individual shows to break even. I don't watch a lot of TV, so I only ever watch one program on CBS, a show called Elementary. I would be willing to consider paying something like $1/episode or $25 for the whole season up front - but that has run for a few years already. For launching a new show with the production value and baseline quality of acting that a commercial audience expects, you probably can't get people to pay for it without spending the same amount of money on marketing as on the production itself. So without the cross-subsidies from advertising it would be quite difficult to raise the capital to finance new TV shows. Obviously you have alternatives depending on what sort of show you want to make, eg you can produce a wacky animated comedy relatively cheaply and launch it on YouTube or somesuch to get your initial audience critical mass. But if you want to do an hour-long serious drama or current affairs or science programming, your up front costs are far higher and you need people to open their checkbooks - your MVP probably costs at least $1 million.