I think the thing with the Diamond Temple is that the normal odds of breeding an ultra rare diamond-type are >1%, so 6 times that doesn't really do much. Even with a 6X increase, it's still lower odds than breeding a super rare. It is deceptive, imho.
I've never bothered buying one because of this reason. Seems like a rip-off, especially since it has to be recharged.
I'm sorry you've invested and lost so much gold.