Infinity-Box - Price-list
1 phone - from 13.50 to 17.50
50 credits -> 17.50 (it max price, if buy only 50 credits)
When you buy 100 ub - 30 usd, 1 phone -> 16.5 usd. but 13.5 will left (45), need buy again 100 credits to unlock next phone?
If see in it deeper - not bad math...