Klose left for an undisclosed transfer fee, estimated to be around €12 M, dependent on his achievements with Bayern. But he had only one year left to his contract left.
As for Gomez, as I said, whilst he's a good player, €30 M aren't exactly peanuts for him and a murmor went through the Bundesliga when the fee became known. Hoeneß even had to defend himself for spilling out that much money.
The fees in the Bundesliga are lower, but the individual class of the players is often lower and Bayern doesn't face much rivalry from other clubs. If you are Cologne or Bremen and have a very good player in your ranks, there's almost only one club you can offer that player to - Bayern. Other clubs won't be able to attract him, won't be able to pay him his dream wages and won't be able to pay a huge transfer fee.
seeing Leverkusen sell them so cheaply to their biggest rivals at the time the summer after being in the CL final.