I'm trying to get my friend a nightmare potion since his nightmare nekota got turned into a green mantis (?) I have 600 CSC but no clue what that's worth.

So, what's the ratio of CSC to sP?

you can always find the conversion rate by checking the price of a 100 credit gift card. right now 100 csc is worth about 11 million sP. so a nightmare potion, which is currently selling in user shops for ~16 million sP, is worth about 125 csc.

Awesome, thanks!

Nevermind :)

The current rate users are charging for this is a little high, IMO. 500 CSC has been pretty steady over the years to be around "the amount of sP you can readily make in ten days" which to my mind would be around 10MsP per 100 CSC right now.

Anytime around Black Friday the price of CSC goes up and sometimes stays up above and beyond this. The price for CSC can suddenly drop over the holidays as folks get gift cards in RL and choose to spend here who want the sP instead, so keep your eyes peeled.