the relevant competitors would be cable television, subscription satellite TV services, and various forms of offline media distributing the same content (DVDs at Walmart for example).
From Pa. Code § 9.2. Sales and use tax changes:
(2) Pay television. Pay television except for ‘‘minimum pay television’’ is taxable. This includes anything charged to a customer for a service other than minimum pay television service. For example, if a cable television customer purchases basic service and in addition purchases a ‘‘pay’’ channel, tax is owed on the price charged for the ‘‘pay’’ channel. Installation and repair service for pay television with the exception of minimum pay television also is subject to tax.