I think that the prices going up has more to do with the CB and Compendium then it does with the magazines. Each month, the utility of those two applications increases as more content is added. In any case, June looks to be a return to form, at least for Dragon, what with a Demonomicon, Class Acts, Ecology of..., and Playing... articles, not to mention two FR articles (I'm assuming the one on bards is a player-orientated one).
The price going up was always a planned thing. I distinctly recell when DDI came out that WotC said multiple times it was an introductory price, and would go up after a trial period. I think six-ish months was a pretty good run at the lower price, not to mention being able to extend subscriptions at the low price up until the change.