Here is what I found when clicking on the
Purchase link:
PURCHASE and LICENSE DETAILS
Please choose one of the following:
Which product is right for me?
JRiver MEDIA CENTER version 9.x $39.98
Switching between versions 8.0 and 9.x
Restoring a license
Previous versions:
MEDIA JUKEBOX version 8.0 $24.98
MEDIA JUKEBOX version 7.2 No longer sold
It seems pretty straight forward to me and I don't see any mention about "upgrade" pricing, let alone it being the only method.
Clicking on the Media Center version 9.x link brings up:
MEDIA CENTER Purchase FAQ
Thank you for your interest in JRiver Media Center. This page will answer questions you may have about purchasing or about a license you may already own.
Media Center 9 can be purchased from the Help section of the program. The price is $39.98.
A Media Center version 9 license will also work with Media Jukebox version 8.0. An MJ version 8 license purchased before December 3, 2002, will work with MC version 9. MJ Version 8 licenses purchased after December 3, 2002, can be upgraded to MC version 9. The upgrade price is $19.98.
It states that MC9 may be
purchased from the help section. This FAQ goes into detail about the purchase process including checking to make sure you are purchasing the correct license.
As another poster indicated, though, the price in either case is well worth it. The $5 difference is less than you'll find from other software vendors that still offer previous/alternate versions.