Ah, where I am soy milk varies in cost greatly.
By watering it down, I simply meant taking the commercial version and adding some water and blending away in the blender to create a thinner product with more bulk. But if you like the consistency, then you wouldn't want to do that.

As far as the homemade tasting less bitter, have you tried adding fruit, maybe even just a banana, if you like them? I always used them in my smoothies with unsweetened soy milk and they made quite a difference. Frozen fruits could also be an option as you could buy organic year round.
I am very sorry about your skin condition, that sounds frustrating and scary, but glad you have found away around it! I too hope you can find a medium that works for both you and your wallet.