The cost of the Warhammer 6R (
http://www.masterunitlist.info/Unit/Details/3488) appears to be off by one C-Bill.
The TechManual's formula: (Structural Cost + Weapon/Equipment Cost) * (Omnimech Cost) * (1 + [Total Tonnage / 100])
Applied to the WHM-6R: 3,543,166.667 * 1 * 1.7 = 6,023,383.3339, which rounds down to 6,023,383.
The value for the Structural Cost + Weapon/Equipment Cost is a bit lengthy, but the only item without a nicely rounded cost is the 280 Fusion Engine, which has a cost of 1,306,666.667 (rounded for brevity per the errata). My theory is that the cost was rounded up before plugging it into the Final Unit Cost Formula, which results in a final value of 6,023,383.9, which rounds up to 6,023,384.