The number isn't quite that high. Consider:

Total Possible - Actual Possible = Total Lost
(36^8 + 36^9 + 36^10 + 36^11 + 36^12) - ((36^6 + 36^7 + 36^8 + 36^9 + 
+36^10)*10*26) = TL
36^6 * ((36^2 + 36^3 + 36^4 + 36^5 + 36^6) - ((36^0 + 36^1 + 36^2 + 36
+^3 + 36^4)*10*26)) = TL
36^6 * (2,238,976,080 - 449,177,300) = TL
3,896,002,369,298,350,080 = Total Lost
[download]

Although 19 digits is hardly a trivial amount (-: