If multiplying the size by 5 means multiplying the cost by 10 (and if this relationship is consistent as size continues to increase) then a 100x size increase is about 2.86 5x-ings, which means a cost increase of about 10^2.86 or about 730, which means that $12M becomes about $8.7B. (Much more than the $3B you suggest and of course much much more than the $300M OP suggests.)
[EDITED to add:] Oops, should have refreshed the page before commenting; I see that OP has already fixed this.
If multiplying the size by 5 means multiplying the cost by 10 (and if this relationship is consistent as size continues to increase) then a 100x size increase is about 2.86 5x-ings, which means a cost increase of about 10^2.86 or about 730, which means that $12M becomes about $8.7B. (Much more than the $3B you suggest and of course much much more than the $300M OP suggests.)
[EDITED to add:] Oops, should have refreshed the page before commenting; I see that OP has already fixed this.