Good morning, John, and a happy hello to you...
I have no idea what a CAC flint marble is, and I don't recall that Peltier made anything that sounded similar to compare them to.
I can compare the above prices to Peltier's prices from about the same period, 1925-28, for perhaps some small insight. (Listed prices for size #1 marbles)
Onyx - $4.90 M - all regular colors, white, amber, green, royal blue, azure blue, purple - Made in size #00 - #6.
Cerise Onyx - $10.06 M - Cerise (red) was much more difficult to make than the other colors, and cost twice as much to produce.* Made in size #0 - #6.
Prima Agate - $20.00 M - Prima marbles had an opal base glass that required special processes and a different furnace, which, when combined with cerise cost four times as much as their regular onyx marbles. Made in size #00 - #5.
Milky - $12.00 M - The opal glass was somewhat more expensive to make than the cerise glass. Made in size #00 - #2.
*Fun fact...in the early years, the cerise glass had to be made into glass sheets first, before it could be used in marbles. Peltier hired women as "strippers", whose job it was to cut the sheets of cerise glass into strips, so it could be used for the marble striping.