How do you determine the value of a HB monthly games?

Well idk the other people but when i buy a bundle game i determine the next things.

-how many times was bundle before
-what tier of the bundle is it
-what's the lower price in steam sales of the game (in case was never bundle before)
-how many of good games have the bundle
-how many people are trading it

and after that i decide how many i want to pay.

example:

game 1 it's bundle for first time and the lower price of steam was 5$, the guy payed 15$ for the full bundle so i will not pay more than 2.5$ depending in the full bundle etc... if hte bundle have a lot of good games i will want pay less because he can ask a bit more for each game.

2€

Supply and demand, pretty much. SOMA was easily sold for 3 keys since people really wanted it and it resulted in high prices. Grim Dawn right now has prices ranging in the 2-4 keys territory, but many sellers are asking prices a lot of buyers are not okay with. WWE 2K16 in theory should be an at least 2-key game, yet you are lucky if you can sell it for 1. Funny enough, that typing game seems to be more popular, even though that is a much smaller niché market.

If I want to play the game, I activate myself. If I don't, I give it away.

Or is this some goofy trading ish?

How good the game is, what price, bundle tier, how much people want it. If I'm completely unsure I might check what others want for it.

humble bundle love applying game theories for their business...

I bought WWE 16 for 2.50$ (fair price in my opinion) and SOMA for 6.00$ (bit overpriced but that's the price it's going for atm) Wouldn't pay more than 6 USD for it better wait for a 75% off IMO.

Just use g2a as a reference. Not all games within any given bundle tier are going to have the same value either, it all comes down to supply & demand for each individual game.