A.I. pays too much for obsolete techs.

[Kingreno]

When the corresponding wonder has been built, AI still pays huse Gold per turn ammounts for the techs. These techs, mainly Music theory and Free artisty, that serve no other purpose then the wonders, were worthless once bach and shake's had been built.
In C3C I got 290gpt from 3 civs total for Music Theory, where I had built bachs ages ago...