Yes, when the prices variation is in a few percentage bracket but here you speak about selling the same pictures 200$ on Alamy and 1 $ or less in microstock agencies.
Everybody here seems trying to get a better return for their pictures, if you sell the same thing at both markets you just muddle the water a bit more.
Is it so difficult to keep some really good photos for the better paying market and help them to make a difference ?
10mp image at alamy = $330 I believe this to be a full extended licence (the biggest from any site, except for buyout) so the equivalent at istock is 100 credits or about $130 to buy the same thing.
still a fair bit of difference

I have over 1000 images taken with 6mp camera on alamy its been over 2 years since I had a rejection for quality.