That old thing is so off though. xD The user who made it was frustrated with the insultingly low prices people were giving their Creatu at the time (her blog mentioned a ginger Vogar that had been on the ACS for less than five thousand tu), so she bumped hers up to overpriced in an attempt to equal it out.

It is very nice guide-wise, but you probably won't sell anything unless you jump into the ACS and get your hands dirty. Prices vary too much? Well if there's a very big difference between the cheapest Creatu and the ones above them, try to buy up the lowest ones and reprice them higher. You'll make a nice profit if they sell for your higher price, and you'll even out the Creatu's value a little.

And even if you don't feel like doing that, the ACS is still your best bet for pricing. Just try going a little above the cheapest Creatu - yours should sell after those do.