360 Marketplace Game "Add-Ons" a scam?

For those of you who have bought add-ons for games, have you noticed their download sizes? I'll bet that most "add-ons" (except extra levels on COD2, Halo 2 etc) are around 108kb. After reading the following, it started making sense. How can you have an entire dungeon in Oblivion be just 100kb?

Here's what game developers and Microsoft don't tell you - you aren't actually buying the content, you are buying a "key" which will unlock content ALREADY on the disc. You paid the $50-60 for the game, yet you pay more for things which should be free (as most add-ons/mods are for the PC).

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Industrious NeoGAF poster "a master Ninja" has done a little digging and uncovered just how big some of the "downloads" are over the XBL marketplace. I say "downloads" because, well, you're not really downloading much. From the size of these files, it's clear you're just downloading a key that unlocks content already present on the disc. Content that you've already paid for by paying for the disc.

Chromehounds
Total price of all downloadable parts keys (1800 points – around $20)
The keys are 108.00 KB each
College Hoops 2K7
2K ReelMaker for College Hoops 2K7 (400 points)
108.00 KB

Viva Pinata
Accessory Packs 1,2,3,4 (80 points each)
The keys are 108.00 KB each

Need for Speed: Carbon
Total price for all the available content keys (7320 points – around $75)
The keys are 108.00 KB each

Ridge Racer 6
36 different cars
The keys are 108.00 KB each

Source #1: Kotaku
Source #2: Official Xbox Forums
Link: Neowin Forum Discussion