BankAlt.com was conceived over a lengthy period and it has gone through several conceptual iterations until it arrived to the current state.
Though the initial concepts also dealt with World of Warcraft professions, the idea was completely different from what you see today. The current incarnation is a very young concept, easier to implement and hopefully more useful to a lot more people.
My idea for the current incarnation of the site came after many frustrations with trying to figure out what sub-components I needed for various crafting recipes/patterns/schematics. A specific example is Frostweave Bags. Since I have both an enchanter (who can provide dusts and essences for cheap) and a tailor, the required mats are always at my disposal but it's a hassle to remember that for 1 bag I need X amount of Infinite Dust and X pieces of Frostweave Cloth.
Wouldn't it be nice if there was some way of calculating how many of these sub-components are needed? Enter BankAlt.com. On BankAlt you will find a list of all professions (with the exception of a few that might be added later) and all recipes within each profession (again, with a few exceptions). For each recipe which has components that in turn have sub-components, you will be able to drill down and see all the base mats needed to craft the item in the main recipe. To use the Frostweave Bag example, you will need 2x Eternium Thread, 12x Infinite Dust and 60x Frostweave Cloth for one bag.
BankAlt.com is certainly useful for my needs. I hope it will prove equally, if not more, useful for yours.