The market prices will continue to ebb and flow as the game and it's community starts to find it's place. Community challenges will throw a grenade into a stable market now and again. It's fairly healthy, but I completely understand how it can be frustrating if one tries to do a nice deed by listing something far under market only to see it resold for significant profit. But that's the risk.
I look at it this way: if a given animal is listed so cheaply that it can be quickly bought up and sold for a significant markup, then the market at large didn't really need the original cheap price in the first place.
And as someone said, it doesn't guarantee the marked up price will lead to a transaction. As I understand it to work, Frontier will often list animals at prices that they set in an effort to control profiteering. This will give new players and those who are short on CC income to get involved and not have to deal with the larger franchises that try to corner the market.
It's too early to say if it's all working as intended, but so far, it seems OK to me.
Invest your 1500 wisely!
