This statement is so abusrdly false that it's not even funny.
They cost that much because you have to not only salvage ascended rings, but also put roughly the same amount of silver into it to even break even. That's before you talk about the demand of the item being used in several legendaries.
Also gonna let you in on a dirty secret. Most people who buy the statted infusion already run CM's enough to use the bigger brother Integrated Fractal Matrix to get their infusions.