I'm thinking of creating some CWs, but the custom wearables creation page only says "a modest price." What does this mean? CSC or real world money? Of the two, how much of which?

the prices vary based off of the size/coverage of the HA. if you go to the CW page under the cash shop drop-down, and click 'create', there is a form to fill out. the prices for each option are listed under the "type of item" section.

Thank you! I missed seeing that.

Just adding to the confusion but if your item isn’t accepted for whatever reason are your CSC refunded?

Yep :)