That projection is a bit much IMO for feeding ten snakes. Here is my rough yearly upkeep(I buy live rats weekly for 8 snakes.)
$1-$2 avg price for rats - Mine personally range from feeding pups through mediums. My rat breeder charges me $1 per rat on average so $8 week. 52weeks x $8 = $416/year for rats. If you are not buying from a supplier other than chain stores or local reptile shops I recommend finding one in your area or looking into breeding your own, you will cut costs immensely here. I realized i would be paying >$800 a year for my 8 snakes if I bought from the local herp shop, now I'm closer to $400 a year.
Substrate - unprinted newpaper. I have personally seen the prices on this range from free to $2. In my experience I use roughly 1 roll per 3 months for my collection. 4 rolls/yr = $5-$8 substrate/yr
water dishes - I use plastic deli cups from fabrikal, I believe i paid ~$17 for 100 cups. you'll have to get creative to keep them from spilling. These are easily cleaned as well as replaceable and should last you a while.
I personally do not use any type of water conditioner for my snakes. I do let the water sit out for at least a day to let the chlorine evaporate off but I do that due to my avid indoor gardening.
I believe that puts my yearly upkeep - electricity at <$500/yr. These snakes can be kept economically, just gotta be creative and use your brain a bit.