So, I had enough sP to start the quest, but apparently after I bought the items he needed, I fell below the threshold. I buy the items in a separate tab, so when I switched back to the original and clicked "finish quest" I received this message:

"I expect a certain amount of sP to be put into my quests. Sadly, you just can't provide that."

This prevented me from finishing the quest I started. Additionally, when I revisit/reload Saggi's page, I still receive that message.

Not a big deal, since I always do Saggi's first, so I went over and completed a Wizard quest to bump me back over the threshold, at which point I was able to turn in my items to Saggi. However, if I didn't have any way to get the needed sP quickly, that would be really frustrating (especially since I already bought the items).

I think that once you start a quest, you should be able to finish it, even if you're under the sP threshold.

It's always been this way and never made sense to me, either. Staff is well aware of it.

Alright then. Case closed. Lock it up, boys xD