The only place within reasonable driving distance from where I live
that will do a MES commercial charges $500 an hour in a twin sea bee.
I figure it may be cheaper to spend the money on a airline ticket and
a week's stay in a hotel in order to get it done somewhere in a Apache
or something on floats for $200 an hour...

Also, would it be best to get the SES first (which is a LOT cheaper),
then spend like 2 hours transitioning to the MES, or will I still need
8+ hours of MES time in order to pass the checkride? In other words,
if you already have your SES and your MEL, is a MES more or less a
formality, or will there most likely have to do a lot more training?
Remember, my goal here is to get the rating with the least money as
possible.