I have around 1600+ materia conversions logged but they don't have the exact #'s its like:
Dated Electrum Ring, STR Materia IV, PlayerName

If this would help you I can email/PM you the results. I made a mod to my parser which collects materia conversions. Since I don't think the base item affects the outcome IE R41~R50 NQ/HQ has the same exact result % so I was most concerned with just what the %'s were to evaluate the market value associated with a type of materia, IE its a 5% chance at on getting healer hand so the cost justifies the conversion % where PIE is a 40% chance on earrings so the cost does not justify the %.