I'm working through these sorts of design/logistics challenges right now, here's my actual numbers below. Note: Not posting the full designs because those go in the Fan Designs forums, right? BUT........ Two 50-ton tanks, roughly analogous to a T-72 or Chinese Type-96B. Alternatives to the Po and the Vedette in the BTU....
Tank #1: ICE engine 4/6MP, LB-10X w/30 rounds, thinner armor.
Tank #2: XL Fusion Engine 4/6MP, Gauss Rifle w/32rounds, heavier armor.
Personnel quantity and cost columns are omitted here, but they are 4 vehicle crew, 1 tech, 6 astechs, and 1 admin for both vehicles, all with salaries from AToW (per the suggestion in CO). I use the Euro currency symbol to denote C-Bills in my spreadsheet. The fuel cost is $1,000 CBills/ton for petrochemicals as per SO pg. 179. All numbers are monthly unless indicated. Units were designed in MegaMek 0.47.0. and key data was hand-jammed into my master LibreOffice spreadsheet.
Nomenclature | Ammo (tons) | Ammo (CBills) | Spare Parts (tons) | Fuel (tons) | Cost incl. Salaries | Annual Cost | Unit Procurement Price |
50t MBT-ICE | 1 | €15,750 | 0.05 | 1.7 | €22,950 | €275,400 | €1,340,500 |
50t MBT-XLF | 1.375 | €20,625 | 0.05 | 0 | €27,825 | €333,900 | €5,646,250 |
As you can see, the maintenance cost delta is ~$58,000 per year, the bulk of which for both tanks is ballistics ammunition. It would take the XL Fusion MBT ~70 years to recoup its significantly higher purchase price. Something like $2.6M of that price is the engine IIRC.
On the subject of range and logistical requirements....I'm working through some conceptual scenarios in SBF to determine what is a reasonable log tail. ICE/fuel cell combat vehicles have ranges of 450-600km, which is enough to move 1 hex.....at the 84-hour, 750km
ACS scale. Topping off the fuel every 2-3 days isn't unreasonable, the crews will need to rest at some point anyway. Pushing people past 36-48hrs of continuous ops is a bad idea.
SBF is 500-meter hexes @ 3-minute turns. The real question is "How far are you willing to land from your objective?" and "How much time will you allow for your opponent to prepare his defense?" If you want your LZ outside of artillery range from the objective, the longest-ranged arty is I think the Cruise Missile 120 @ 153 SBF hexes (~75km). Anything smaller than a cruise missile maxes out at <16km. If you are confident the defenders won't be lobbing Iskander-Ms at your LZ, you could probably land ~50km from the OBJ or less, giving yourself some wiggle room in case they come out for a meeting engagement or spoiling attack. If you stick with this style of assault, the need to drive >600km unrefueled should become moot, and the cost of refueling, even accounting for POL trucks and supply personnel, should barely be a rounding error. Note: I haven't finished my SBF Formation TO&Es with all logistics vehicles yet so I don't have Campaign Ops costs worked out for discrete company-sized units completely....just the bulk of the combat arms stuff. I might have to totally re-jig some vehicle designs as a more thorough reading of the SBF rules seems to indicate you can't really set up a Support By Fire position in an adjacent hex and really capitalize on your Long Range fire values. You can only shoot from an adj hex if you can do Indirect Fire or Arty attacks. Unless I'm reading things wrong....
But anyways, I'm willing to skimp on PROCUREMENT cost as the operating expenses of ICE or Fuel Cell vehicles, outside of the brutal "ammo usage during training" part fit within my tactical/operational doctrine. I'm only considering Fusion on certain vehicles where I REALLY wanna stuff maximum lethality in my 50-ton light vehicle bays.