I guess it was nice while it lasted. Earlier I wrote about why KLM flight bundles might not be a bad idea at all to use. And apparently, many other people found out too. They have now increased in price. And not by a few percent.
I checked the bundle I was looking for last time: between Amsterdam and Venice. I recall that it was just slightly more expensive per return than the cheapest return you can book (99 euro), probably around 106 euro per return.
When I just checked the same bundle (20 single flights, 2 persons, least flexibility, 180 days or more advance booking) the price per return flight increased to a whopping 202 euro. So when you're looking for cheap returns, you'll have to revert to early booking and special actions.