Value of Gifts Sent correlated to current Steam Prices?

If a game is in the list of bundled games, then it is treated as bundled.
The list is updated manually by human beings, so "it" actually doesn't "know" ;)

you can find the list of bundled games here: http://www.steamgifts.com/bundle-games
(faq -> "bundle games" almost at the end of the text)

if a game get bundled first time, it will appear here in this list. probably it will appear much later, but gets dated backwards so all ga's created after it got bundled, will get decreased in the value for the level (sry for my bad english^^). so you can loose some level this way^^
also important: if the price gets reduced drasticly (95% or more - in difference to the normal american price), it will get into the list as well