Not sure if its cheaper. The features of the sybex version are equal to the extra edition of conitec as far as I know.
However when you buy your 3dgs from conitec you will be registered and get a personal key file.
That one is missing when buying a sybex version but you need it to update and is the only thing that makes your 3dgs version a "valid conitec" version.

So if you want the latest updates etc. you should buy a conitec version.