When i started playing STO in february the conversion rate was around 180-184 dil for 1 CP. After the cardassian lockboxes were released the price went up to 240-248 dil for CP. When the Oddy pack was released it was something about around 280-284 dil/ CP. Ferengi lockboxes pushed the price to around 310.
I noticed an average increase of 60 dillithium when something new is announced, and if we take as a starting point 310 dilithium/CP, i can guess that the final price 12 hours before the carrier will be released will be around 370-380 d per CP.