Ewe, I have a lot of birds so I have spent literally thousands on food and supplies, not even counting the birds.
I'll give my estimate for, say, one sun conure:
-Suitable cage: $50 on up. I've picked up decent used cages at yard sales and thrift stores.
-Playstand: Free on up. I've made my own out of safe branches from my yard with plastic storage container lids as the base.
-Perches: Free on up. Again, branches from my yard.
-Toys: Free on up. For the last many, many years I've rarely bought bird toys from stores. I'm big on safe children's toys from thrift stores and stuff from the 99 cent store. I also really prefer new foods as "toys" like entire broccoli stalks, half apples, unique seasonal fruits & veggies.
-Initial supply of food: $20 for a 5# bag of seed; $15 for a 4# bag of kaytee pellets. I think that will last one sun conure about a month.
-Initial supply of treats: minimal on up. Ok, I do buy Ducky Nutriberries which is about $10 for a 12 oz bucket ; otherwise I'm big on the fresh stuff and cooked mixes for treats.
-POH, Parrot Operators Handbook, a book about your species: Library. I like to preview before I buy. Some of them really suck in my opinion. Our county library has where you can request books from other library systems. I've been able to request some excellent books that were in college libraries.
Some additional optional items may include:
-Carrier: $5 I make my own out of storage containers
-Water bottle: $5
-Vitamins: Hmm. . . zero unless your vet recommends it. New buyers of my birds I don't even mention vitamins. If they're feeding the pellets and then the fresh foods, cooked mix, sprouts, then I don't want them over vitaminizing w/out veterinary advice.
-Nail trimming scissors:?? I use human nail clippers. I've seen the little curved cat claw clippers at the 99 cent store.
-Quickstop (should really be in required list): $5-$10. I prefer a product called Clotisol. You can't use quickstop for general wounds to stop bleeding, you can with Clotisol. I ordered the stuff online. It's supposed to be safer and less caustic than quickstop.
-Training aids and materials: ?? depends what you want to do with the training.
-Cage cleaning sprays: $2-$5 for a gallon of bleach. I take my cages outside and hose down. Then disinfect w/ dilute bleach solution. Given the spectrum of stuff bleach kills, the safety of bleach, and the cost it's what I use. Since I breed birds, I've researched disinfectants big time. Bleach keeps coming back the winner.
-Spare perches and toys: whatever you want to spend.
-Additional food bowls: less than $10. Thrift stores, 99 cent stores, yard sales. I love ramikins.
-Initial vet check up: Hopefully where ever the bird came from gave a free initial exam. Then the testing can run a couple hundred dollars through the vet. Or if you feel like you're a competent person to do some sampling yourself you can get quite a gamut for less than $100:
http://www.avianbiotech.com/Pricing.htm