why the first gen is more expensive than the second?
1st generations are just that. The first generation offspring of creatures. The longer the generation, the less expensive the creatures are. There is more demand for 1st generation creatures than longer generation creatures. Therefore, the difference in prices.
How could a solar hippogryph worth the same as a fire gryphon?
They are both hybrids. That is probably why some
price it the same. People have different prices for creatures. Not everyone would sell Solar Hippogryphs for the same price as Fire Gryphons.
How could a chimera worth 50k while a capricorn only 1k?
A Chimera is a hybrid (Ibex x Manticore). There were a few parentless Chimera around before the crash. Now there are more of them. So a parentless hybrid would go for 50k while a bred Capricorn would go for around 1k.
What's the point of collecting only 1 species??
Personal preference? Many members play the game the way they find it interesting. Some collect only 1 pair of each species, some collect armies of certain species, some simply hoard as many as they could possibly hoard. It's how some members play the game I suppose.