I'd guess that the reason their bribes were higher isn't because they had more power, but because they had more money. If a politician is making 50k, a 10k bribe would be significant. That same 10k is a drop in the bucket for a tv station owner with millions.
That analysis is partly true, but it is not the main reason. In Peru at the time, whoever controlled the media controlled the thoughts of the people. The politicians have always had a disconnect with the people, and as such, had never carried true political weight from their voters. Ironically, the government was so corrupt, that the job of the media was to provide the checks and balances because they did carry more political weight than any single politician. The main political media venues that were the most serious, had the most integrity and stood against the government were in 1) printed form and 2) not free. In a country that had (still has) high illiteracy rates and where most of their population is below the poverty line, this was a problem. TV is free, and although some people could not read, they most certainly had a TV. Let me disclose that being the son of a politician that had to escape Per because of Montesino's henchman and being lucky to still be alive after a "little" failed bomb incident and various other things, I am glad that son-of-a-bitch is rotting in a prison.
Interesting thought, but do you know any poor politicians? I don't. I certainly wouldn't expect poor corruptible politicians in a country full of corruption.
This is why fines and suchlike should be a function of income, rather than a set rate. I think they do this in sweden, people get speeding fines reaching into many thousands of dollars.
In my country politicians will ask you for a higher participation in a business than a VC.