My gut tells me that these mics will deliver a level of quality commensurate with their price point. I don't know that you would be disappointed with these, but I also don't know that you would think you got a great deal on these ("Hey these sound like $400 mics, but they cost me $70").
The one thing to understand about Monoprice is that they are not putting the huge mark ups on cables that the big box stores do which is why their prices are so much better than those big box stores. Cables are for the most part, a commodity. The mic market is completely different from the cable market - measurable quality goes up with price.
If you do decide to try these out - give us a review.