Crafting SP Variance

[tymora]

While the individual SP from each item varies a lot, if you take the average you'll find that it is about half of the base physical exp given (After all the patches...).

So if you consider AVG SP gained, it is effectively static. As for the actual SP given, you can think of it as following a normal distribution about the AVG SP, i.e. it is random.

E.g. Same rank recipe gives 500 exp. AVG SP will be 250, and is independent of quality gained and durability.

Don't believe me? Just take down the SP gained for a single grind session and you'll see it.
If you want, take down the physical EXP gained too as a cross reference.