Well, I have 61 smithing on my main.
I have 21M, And If you buy steel bars, And RSBOT make
cannon balls, You can get 86 smithing in a few days and make
like a 5M profit.
For 99, I would estimate 50k Steel bars + the 31K from 61 -86.
So, You would probley end up spending the 80M like he said,
But you will make a profit.