I would definitely check ebay and craigslist first. You can find tons of stuff in great condition that is much easier on the wallet. Also, if you need help finding anything just PM me and I'll be more than happy to help.
Halter - Around $20
Bridle - $30-100 (Depends on material and quality)
Western Saddle - $500-$1500 (I would definitely go used, they're cheaper and already broken in)
Saddle Pad - $30-100 (I'm not very familiar with western pads so I'm not sure)
Bareback Pad - $50 ?? (Again not sure as I've never bought one)
Boots - $50-100 (SMB's are really nice
Hay - Not sure because it's included in my horse's board
Farrier - $50-175 (Depends if your horse is barefoot or not and if he needs anything extra)
I'm not sure how much I spend every year, but I'm sure it's outrageous!!