That bill should not have went up $95! A 400w HPS should cost roughly $20/month on an 18/6 schedule depending on where you live and the price of elec.
BTW: Nice looking plants you got there. If they are anything like the bagseed we get aroung my way, you might end up tieing them buggers down depending on how much height you have. I have grew out some bag-seed quiet a few times and they triple in height after flowering. Heavy sativa. Also, flowering time is the time to NOT let your temps get out of control. You do not want fluffy/airey buds that weigh nothing and take forever to prune. Ask me how I know.... Good growin, keep it up.