Hmm, there's a whole range of prices, and I can only offer the costs in British pounds sterling (GBP), since I buy everything in the UK - everything costs far more in the big resorts.
You can get a pretty good board and bindings for around the £250 mark. They'll be new and unused, but maybe last year, or the previous season's equipment. Nothing wrong with that, very little changes from year to year except graphics.
Salopettes (pants) will set you back from £80 - £180, and a jacket will cost roughly the same.
If you already have any mountaineering gear, then remember that you can use them as well - particularly the jackets. Pants might be a slight issue, since they need fairly baggy legs to go over the boots.
Boots will set you back between £110 and £190. Make sure you try them on first, different brands come in slightly differing shapes, and you need one that fits your foot perfectly, and locks your heel in place. If you have a boot where you can lift your heel up from the sole, then you're going to really struggle to control the board when riding on the toeside.
Gloves, it varies. Snowboard brands tend to be pretty expensive, and actually not very good. I stick to moutnaineering gloves, cheaper, and far more water resistant and harder wearing. Expect to pay about £25.
Helmets vary from about £40 upwards.
Goggles have a HUGE price range, from the cheaper £40 ones, right up to crazy expensive ones. Just pick something in your budget.
If you're just starting out, then I'd suggest renting your equipment. You may find that it's actually not for you, after a few sessions, and will have avoided spending a fortune on unwanted gear.
By renting, you can also try out a few various options before making the decision on what "kind" of board and equipment you want.
For example, you may want a nice soft board for jibbing (grinds, rails and pipes), or a super-stiff board for some freeriding off big drops at high speed.
Also, remember to get some tuition, at least to begin with. Some of the methods of board control aren't exactly intuitive, such as twisting the board, or sinking lower down to shed speed.