What really changes the value is when you start buying 100 cost energy refreshes. If you were to buy two 50 crystal refreshes and just one 100 crystal refresh, the 1,400 crystal cost for cuffs is right in line since you would farm the 50 salvage required 55% of the time with the 1,400 crystals.
By the same measure, the 1,274 crystal cost of a stun gun component is a value purchase since you would farm the 50 salvage only 27.8% of the time.
Edit: Obviously buying more than one 100-crystal energy refresh is not what you want to do in a strict gear farm sense.