Kent:
Prior to January 31, 2013 Windows 8 regular or in some cased RT was apparently generally available by buying a new computer with factory OEM installation. There was a LOT of confusion. Most stores sold only Windows 8 Pro.
Windows 8 Pro was capable of upgrading from a previous version such as Win 7, Vista, XP. Win 8 regular was not generally available but I did see it on sale in Costco. Staples and Best Buy wouldn't offer it for sale.
Win 8 Pro, as it implies, is more for a professional enterprise and not a home owner/user in general. However, Win 8 Pro contains an enhanced security measure BitLocker, an encryption system for enhanced security in the public, multi user, network environment. It further has capabilities to allow connections to TV and to download videos. Further if you want to buy the add on application of some music aspects it can only be done from Win 8 Pro and not from Win 8 regular RT.
Generally Microsoft had staged various levels of applications depending on user requirements/desires. For example the tablets and notebooks with limited screen space are trimmed down versions of Win 8. The add on music aspect is a GB hog. So actually they are not selling you something that you may not want. It's like buying a car standard with the many options, Leather seats, special metallic paint job, sun roof and so on.
Indeed there are some things that you can do with Win 8 Pro, day to day, that you cannot with Win 8 regular.
After January 31, 2013 the scenario changed. Win 8 regular is now generally available in some stores for $119. Win 8 Pro is $199.95.
Costco was selling the both versions in January. Today I checked and they have dropped MS Win 8 entirely from inventory. No longer handling it at all.
Staples told me that they had been loaded up to the eyebrows with inventory. Microsoft marketing forecast a land office boom of people lined up outside at midnight to crash the doors and it never happened.
Sometimes it works out and sometimes it bombs.