Just to show: For a stage 3, if you buy each dragon claw for 38bi, you will need ~4370000 NCoins that means ~54.650 dollars. If you buy each for 20bi (improbable -near impossible- in the current game situation), you will need ~28.750 dollars. -It doesn't count the other necessary items. (r-gem, elcyum...)
If you want to make the math for yourself, use these numbers to avoid too many 0.
1000 = 1T
1 = 1bi
0,002 = 2kk