Blanco's option was for $1.24 million, and we already discussed the possibilities there. It seems the team is perhaps wanting to go with someone a bit more capable of backing up Montero in the event of an extended absence. Whether that turns out to be Wil Nieves, or someone else, will be seen in due course.
The case of Lindstrom is a little more interesting. He was originally acquired from the Baltimore Orioles in the trade for Joe Saunders, and performed pretty well, posting a 2.53 ERA over 12 games for the Diamondbacks. His option was for $4 million with a $200,000 buyout. While that option does seem a bit pricey, you can make the case that Lindstrom would have been a cheaper choice for Arizona than bringing over Heath Bell from the Marlins.
However, worth noting that the Diamondbacks do remain able to negotiate with and sign both players if they wish, bringing them back at a lower price if mutually agreed.