I can't remember exactly but it either costs 100 CP or 250 CP, I think its 250 though you do get some CPs in exchange whenever the custom is used. It might be every few customs, from from time to time I get +25 CP for the uglies public customs. For example:
Year 14 Day 251, 20:58 Star Wars Combine + 25 Public Image Purchase
Edited By: Lilith Delcroix on Year 14 Day 257 13:37 ____________
Moons can't fly.
--> Lvl 5 FI Operator - Free Service <-- +++ Holocron Article +++
I believe it was 250 CPs to get a public custom on your ship before the change to the system. I'm not sure if it is still that cost to upload one for public consumption, or whether they are all 500 CPs to upload now.
However Lilith is correct and you get 25 Cps each time it is used.