Netflix built a huge infrastructure of distribution centers, maintains a huge inventory of product, ships physical discs all over the country, and yet can profitably rent BD releases to me for about $1.50 per title if I watch them promptly and get the full 8 per month my mail service will support.
Redbox built a huge infrastructure of physical machines, set up a billing network, bought the discs, transports them around, maintains inventory, etc, etc, for $1.50 for new-release BD's and is also profitable.
So why can't streaming services price a single HD stream of the same titles for less than $4-5?