It is not an activated ability, so you don't "activate" it. Yes, it has a cost, but it's not in the (cost): (effect) format all activated abilities follow.
It is a triggered ability. It triggers only once each time you activate an loyalty ability from Chandra. When this trigger resolves, you can either pay or not; if you do, it copies Chandra's ability. It's not "pay , copy it X times" or "for each time you pay ", so you can only pay 1 per Regulator per Chandra ability.
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