Now just a reminder I am not trying to beat you up on it if you know what I mean xD Not trying to diminish your values or games. Just trying to give you a better understanding of pricing and how people get to them.
Ok so the first thing I notice is that you have all the store prices on your game list. This is pretty much what drove me to try to help you since it shows clearly that you are not aware of other things like bundles or giveaways or sales , etc.
As a first suggestion I would say look into downloading "Enhanced Steam" plugin for your browser and/or client. This overlay provides additional info on each game like: if it was in a bundle , when , how much , etc.
As you can imagine being in a bundle, sale or giveaway tends to depreciate a game's value substantially based on the price of the bundle mainly and its popularity.
I'll give an example of this which should clear it up fairly well.
Let's take this game http://store.steampowered.com/app/31290/ (Back to the Future The Game by Telltale). Its currently for sale on the steam store for 19.99
Its also available at Humblebundle.com on their bundle. Its available as a Tier 1 bundle which costs 1 dollar for Back to the Future + 4 other games. When you take this into consideration the value of the game is clearly not 20 dollars but closer to .20 cents after all the bundle tier is 1 dollar so you divide by the number of games on that tier and that gives you a good approximation of value.
Now that also applies to Tier 2 and even Tier 3 games as a way to figure out their value. These values might change a bit or a lot depending on which tier the game was in and what prices it was and imo most importantly when the bundle was and if there was another one after it with the game. After all. If it was only bundled once and it was over let's say 6 months ago. It won't be as available for trade with users as something from a month ago.
You also have to remember a LOT of people buy bundles and sometimes even multiple ones.
You can keep track of bundles and giveaways fairly well by keeping an eye on a site called Epicbundle.
If you have any questions feel free to ask.
STEAM: (WorldWide)
1.- Total War: ROME II - Caesar in Gaul (DLC) - 2.50 Dollars
2.- Borealis - 2.50 Dollars
3.- Boxes with Guns - 2.50 Dollars
4.- Pirates of Black Cove - 2.50 Dollars
5.- Commander - Conquest Of The Americas - 2.50 Dollars
6.- Talisman: Prologue - 2.50 Dollars
7.- Joe's Diner - 2.50 Dollars
8.- The Detail Episode 1 - 2.50 Dollars
9.- Fearless Fantasy - 2.50 Dollars
10.- Street Racing Syndicate - 2.50 Dollars
11.- Iron Grip: Warlord - Scorched Earth DLC - 2.50 Dollars
12.- Hero of the Kingdom - 2.50 Dollars
13.- Postal - 2.50 Dollars
14.- Weird Worlds: Return to Infinite Space - 2.50 Dollars
15.- Afterfall Insanity Extended Edition - 2.50 Dollars
16.- Deponia - 2.50 Dollars
17.- Gravity Badgers - 2.50 Dollars
18.- Really Big Sky with Soundtrack - 2.50 Dollars
19.- Anomaly: Warzone Earth - 2.50 Dollars
20.- Knights and Merchants HD - 2.50 Dollars
21.- Orbital Gear - 2.50 Dollars
22.- Epigenesis - 2.50 Dollars
23.- Murder Miners - 2.50 Dollars
24.- CastleMiner Z - 2.50 Dollars
25.- Of Guards And Thieves - 2.50 Dollars
26.- The Sun and Moon - 2.50 Dollars
27.- Aveyond: Gates of Night - 2.50 Dollars
28.- The Last Remnant - 2.50 Dollars
29.- Murdered: Soul Suspect - 2.50 Dollars
30.- Yosumin!™ - 2.50 Dollars
31.- Shofer Race Driver - 2.50 Dollars
32.- Prismatica - 2.50 Dollars
33.- Deadlings: Rotten Edition - 2.50 Dollars
34.- Hatch and Slay - 2.50 Dollars
35.- Betrayer - 2.50 Dollars
36.- One Finger Death Punch - 2.50 Dollars
37.- Warmachine Tactics - 2.50 Dollars
38.- Warmachine Tactics - Mercenaries Faction 2.50 Dollars
39.- Kraven Manor - 2.50 Dollars
40.-Broken Dreams - 2.50 Dollars
41.- Back to the Future: The Game - 2.50 Dollars
42.- Sam & Max: Devil's Playhouse - 2.50 Dollars
43.- Puzzle Agent - 2.50 Dollars
44.- Puzzle Agent 2 - 2.50 Dollars
Steam: Available in this countries: Armenia, Azerbaiyán, Bielorrusia, Georgia, Kirguistán, Kazajstán, Moldova,
Tayikistán, Turkmenistán, Uzbekistán, Ucrania, Rusia:
1.- Faerie Solitaire
ORIGIN: (WorldWide)
1.- Batman™: Arkham Origins DLC - 2.50 Dollars
2.- Plants vs Zombies Game of the Year Edition - 2.50 Dollars
DESURA: (WorldWide)
1.- Hunter´s Trophy 2 - 2.50 Dollars
2.- Ski Park Tycoon - 2.50 Dollars
3.- Boxes with Guns - 2.50 Dollars
4.- Heroes of Steel - 2.50 Dollars
5.- Sanctuary RPG - 2.50 Dollars
6.- Whitewash - 2.50 Dollars
7.- Always Remember Me - 2.50 Dollars
8.- Raiden Legacy The Return - 2.50 Dollars
9.- Arson & Plunder - 2.50 Dollars
GOG: (WorldWide)
1.- Dracula 4: Shadow Of The Dragon - 2.50 Dollars
2.- Tyrian - 2.50 Dollars
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Wishlist: http://steamcommunity.com/profiles/76561198000109148/wishlist