for making +13 you need 300.000 cps
for making +14 you need 600.000 cps
for making +15 you need 900.000 cps
for making +16 you need 1.200.000 cps
for making +17 you need 1.500.000 cps
for making +18 you need 1.800.000 cps
for making +19 you need 2.100.000 cps
for making +20 you need 2.400.000 cps
for making +21 you need 2.700.000 cps
Every +n working i test it on my own items
if you count all that cps from +13 to +21 they will be 13.500.000 cps
you need 13.500.000 cps per +21 item.I didn't count making items from normal to +12 super 2 soc super gems but its around 200.000 to 250.000 cps =)
i wish i helped ya ppls =)