Lessee... so with those numbers, upgrading an Erika MCD-1 so it's functionally equivalent to a Fairlight Excalibur would cost 5 x 4 x 8,000¥ + (2x2 + 3x3 + 4x4 + 5x5 + 6x6) x 7,000¥ = 20 x 8,000¥ + 90 * 7,000¥ = 790,000¥, which added to the 49,500¥ of the Erika MCD-1 gives you a total cost of 839,500¥, or roughly 2% more than buying a Fairlight Excalibur outright, in addition to requiring a whole bunch of rolls. Seems balanced.