Dragon Orb Sheet

First = means the amount of 1* orbs needed for that particular dragon orb, the : indicates the total amount of 1* orbs needed if you're starting from +1. Here's a linear way to put it:

1* = 1(1*) : 1 total
2* = 4(1*) : 5 total
3* = 10(1*) : 15 total
4* = 25(1*) : 40 total
5* = 60(1*) : 100 total
6* = 130(1*) : 230 total
7* = 215(1*) : 445 total
8* = 405(1*) : 850 total
9* = 750(1*) : 1600 total
10* = 1370(1*) : 2970 total
11* = 2525(1*) : 5495 total
12* = 4645(1*) = 10140 total

All you need to do now is multiply the current price of 1* orbs by the number and you'll get the average cost of upgrading to the particular level. Note that there are certain occasions where simply buying an upper grade dragon orb is cheaper than 1* orbs such as the 10* in the cash shop.