Regulation cost is generally underestimated because they don't include the discouragement regulations place on businesses from starting or expanding.
But this is comparing the Bush administration to the Obama administration. It doesn't have anything to do with any underestimation of regulatory costs. Basically Obama has been the same as previous administrations, as opposed to what we hear at Republican debates.
Maybe, but there's really not enough information in the article to say how this comparison was made. My sense is the figures they are citing for both administrations are much too low. And then you have things like the health care reform law, which was been legislated, but we aren't seeing the regulation costs yet due to the implementation timeline.