I typically look at time + materials for crafts. With services, I look at time and compare with what other people are charging. I've done simple mending at an hourly rate, because it just isn't that difficult. Sewing from patterns I charge a bit more for, and I've done at least one pattern that I decided was too fussy to do again. But basic skirts? Still pretty easy.
I pay a lot of attention to difficulty and time. With poetry, I can afford to sell it relatively cheap because I write it fast. I'm still making better money than I would from most magazines, because poetry in the mainstream pays shit wages. You can get a poem from me for less than a paper book -- smaller product, but based on your prompt or maybe you just picked something you liked from a thumbnail. Writing fiction takes longer, so I tend to charge more. Editing is mostly charging what I can get, not what I'm worth. The only place I make an hourly rate suited to my experience level is poetry.