The trade with Bergdal was 5 prisoners who were basically worthless to either side - low to mid level grunts who would probably rot in our military prison system forever because they knew little worth extracting and did little worth prosecuting, and who just ended up in forced labor prisons over there anyway.
The lower trade for Bergdal isn't really surprising. With jouranlists, it's most often their employers who pay the ransom. When you're demanding ransom from the US military, it's much more likely to be paid in bullets than dollars, but prisoner exchange is a long standing practice of war that the US has participated in since before it technically existed.
That also involved a different group - Bergdahl was held by the Taliban, not IS. They have different goals and different needs, both of which mean different demands.
It's worth mentioning that, according to USA Today, the 100 million euro demand was never taken seriously. Huge demands like that were a common IS opening gambit - they'd demand a massive sum, and then take a much smaller one after negotiation. In this case, however, there was no answer to attempts to open the negotiation, no second offer, no counter offer, just silence. There have been instances where ransoms were paid to IS, but they were usually on the order of a few million, not hundreds of millions (GlobalPost was apparently prepared to pay 5 million in this case - the USA Today article I read is ambiguous whether this was dollars or euros since there's a lot of unit mixing going on in these reports), and at least some of the prisoners were executed after payment anyway.
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