The first thing you could try doing is getting into a trade circle to get you some bonuses and changing your government to monarchy.
I have over 7000 infra and this has hardly affected me at all, I don't understand what you are complaining about. I lost about 10k ns, rose something like 3% in the rankings and everything is fine. My current trade set up gives me around -40% infra purchase cost, and -25% infra upkeep cost, combining that with labour camp swapping, factories and an interstate system infra is profitable, at your infra level it will be for at least another thousand or so.