Good question (this is in the latest SVN version, in case people are wondering what the heck we're talking about). The problem was that at 5%, the AI was NEVER building the above listed buildings (see my question in
http://forums.civfanatics.com/showthread.php?t=341521). The AI does build them at 10%. There are other ways to deal with this -- changing the AI valuation formula or making the buildings cheaper, but just making the buildings give a bit more "bang-for-the-buck" was worth testing.
The real question is -- are these buildings valued correctly? Does the cost match the benefits? I assume more people have experience playing with the relatively early brewery and weaver than with the other ones. Are these buildings worth the cost at 5%? 5%

may not be a lot when your economy is in good shape

science: above 70%).