I've been working on a website to calculate the cost to craft various items. You enter in values for raw materials, such as Thalasite Ore, Sarleaf, Dust of the Void (default values are provided), and it then figures out the full cost for everything. The raw material prices are stored locally in a cookie, so you don't have to enter them every time.
You can use it as a crafter to figure out how much to charge for an item, or as a buyer to know what to expect to pay. Or finding the cheapest recipes to break down for Rune mats (Fine Fabled Cape seems to win).
It is still bare bones as I haven't added any graphics. And I haven't done Rune upgrades yet, not sure they are needed since they are all just rune + amender.
Would it be possible to enter alternate costs for crafted components in a recipe? For example Thalasite Dream Alloy uses Strands of Draum. It'd be nice to be able to plug in a market price for the Strands of Draum instead of using its base crafting cost since I'm not able to craft it myself. Maybe a checkbox next to the item to swap between prices or something.
Unfortunately the way I coded it up, every "item" is a recipe with 0 or more "items" to make it, if it has 0 components it uses the user submitted value, if it has 1 or more, it recursively calculates the cost of each sub-item. So there is no way to have an item be both user supplied and calculated.
I, too, use a big spreadsheet that takes a raw dump of current prices for mats and crafted items from my shard's AH and calculates what's profitable to make, assuming purchased mats. Took me a while to set it up, but it was worth it in the long run.