It really DOES depend on condition, and what sort of condition you hope to get out of it. If the playfield and cabinet are in acceptable condition to you, then you've avoided a LOT of cost right there. Are all of the plastics there? A new plastic set, for example, usually runs around 150 if they're available.

WW is a 3 flipper game, so as far as mechanics go, you really shouldn't need to put more than 120 into rebuilding the flippers (and that's all new mechs). You can add a lot of life to other coils (like the 6 pops) by changing out the sleeves (dirt cheap, like .30/sleeve). If that, along with adjusting switches, doesn't get you the desired effect, you probably want to follow Vid's repair guide on rebuilding pops:

http://pinside.com/pinball/forum/topic/vids-guide-to-rebuilding-pop-bumpers

Now, electronics are cheap, if you're comfortable with your (temp controlled) soldering iron. If you don't have any desire to trouble shoot or repair a board if needed, I think a new MPU runs about $200 on average. There are places you can send it off for cheaper (I think), but that's no fun - fix it yourself if you can.

So,... what's wrong with this WW?