Computer at 200$ are ok (oceanis or aeris Manta), dont forget bags (~150), maybe tank (150 to 300) while this one can be rented.
Light probably ~100$.
weights if you buy your own and are lead bags : ~50+
wristle, smb, plate, retainers and various crap you may not need in the long run: ~100$
Make a list of all the material you'd need, spend some time on this board to check different pros and cons of various material and set-up.
Then go and browse at your local dive shop, then online (leisurepro, scubatoys, diveriteinscuba, divegearexpress, and many others.
OW training probably ~ 350-400$, then if you progress to advance and rescue, it will be another 300-400.
You'll have to dive as well, and if boats trip, probably few hundreds go fast.
At the end, it is a decent amount of money, and for sure more than what you thought at the beginning.
I made a list a while back:
http://www.scubaboard.com/forums/new-divers-those-considering-diving/301167-newbies-beware.html
and many others have gone through similar studies.
goog luck.