You couldn't be any more incorrect.
The retail version of Killing Floor was released out in 2009 with the following:
- 5 maps
- 9 enemies
- Around 15 weapons, not sure
- 6 player avatars
- 6 classes with 6 class levels (0-5)
- 4 difficulties
In addition, Killing Floor has since been provided with free updates offering:
- 17 new maps
- 1 new enemy type
- 3 new models for all 10 enemy types for the holiday seasons, complete with their own unique voice acting
- Around 16 new weapons, not sure
- 1 additional class level, level 6
- New player avatars unlocked by achievements, events or paid dlc
- 1 new difficulty
In total, Killing Floor has:
- 22 maps
- 40 enemies, 10 types
- 31 weapons, plus 3 can be used akimbo
- 6 classes with 7 levels (0-6)
- 38 player avatars
- 5 difficulties
Killing Floor also contains a wide choice of white listed maps and mutator support to allow you to level on the community's custom creations.
Addendum
Tripwire have offered a great free content service with Killing Floor with a smart business plan. Alongside the updates and STEAM discounted deals, Tripwire released cosmetic player avatar DLC alongside these updates which are/were typically priced at a dollar or two each. These encourage the player to spend as a cheap incentive to those who'd to show Tripwire gratification for these updates. It should be used as an example for all developers, especially in this day and age of bad DLC.
To say this game has a lack of content is a very big insult to the hard work the small development team have put into it for almost 3 years.
Oddly enough I do not believe there is a Killing Floor thread, let me rectify this by splitting the posts.