I have done some experimenting lately, and found that when you put items worth around 700k+ in the trading post and say "First to offer gets it" You see that people offer things that are worth more than what it is worth.

For example:

I put up 2 Baby PBs, and someone offered a pirate draik egg and 800K NP. They were not first, but you accept it anyway. You gain about 2.5 million neopoints right there.

I gained 15 Million yesterday!