Formula doesn't go on sale often but here's a deal that can lighten the load a little. Get a 6 pack (8 oz. ready to feed bottles) of Similac Sensitive at Babies R Us for just $5. (Regularly $10.99).
If you're near a store you can choose in store pickup for free or if you go through Shop Runner you'll get 2 day shipping for free. You can also sign up for a 30 day trial. I have had Shop Runner for 6 months or so and love it. They've been adding quite a few stores lately and I get my money's worth through Babies R Us and Toys R Us.