Cheapest price I have seen for land I wanted was 79,000 and the seller wanted a bunch of tech too. In most cases tech and land swap is required along with money. If you want to make 40,000+ per turn just go capture all of India. So far capturing India is the fastest way I have found to make massive wealth in trade and taxes. So far with my current Dutch faction campaign I rarely fall below 250,000 cash in my bank. I havent been able to buy New York yet. They just won't sell. The most I have offered so far though is 100,000 and some tech. Maybe I'll try 150,000 just to see if they'll sell. At that price though I think I'd rather invade considering I've already taken France and Spain and all their colonies.