Its getting more used since double ruleset because, as mentioned, Sneak is getting popular again and Hydra is one of the best card to counter double Sneak. Being a Beta Neutral Legendary means it is rarer than other Alpha legendaries and hence Hydra had been on the high side since the beginning. But for the purpose of investing, I think GF is still the best bet. Look at gold Elven, she is super cheap compared to the regular one.