As a former VAR (Value Added Reseller) and an authorized Corel dealer I can state to a 99.999% certainty that OEM is as described by the Corel site and that nobody can legally sell OEM versions without being the Original Equipment Manufacturer or their designate. Further, OEM versions can be registered, supported and are eligible for upgrades. Finally, there is no way, no how that anyone is receiving discounts from Corel that would permit them to profitably sell the Corel X4 Suite for $100 and change.
Of course, you're welcome to supply these sites your credit card. They know how to imitate the look of anyplace they want to look like so you will think you're on a safe site to give out your information. Just don't be surprised when some Nigerian is giving his girlfriend a nice HD TV at your expense.