http://i.imgur.com/0ioRebO.png
The ontos has a BV and cost discrepancy here, even though all of it's parts are at F rank and the cost modifier for F rank parts is set at 0.9. I tried increasing the modifier for F rank parts to 1.0, but it still could not match the actual cost.
While I can't find it right now, there is already an open report regarding this. It's because not all costs are fully implemented in MekHQ.
Setting as duplicate, but leaving open until the duplicate report is found.
The BV discrepancy is interesting as that should be calculated using the same method in Entity. The cost difference is more complicated than some costs not being implemented. Costs in MM and MHQ are calculated using different methods. In MHQ, we add up the cost of all the part objects owned by the units and multiply by the unit multipliers from the Tech Manual. MM uses a different method and what you see reported in the buy unit dialog is the MM method. In most cases they give pretty close values, but that one does seem off. I will play around with it and see what is driving it because it doesn't look like there is any particularly complicating equipment in this case.
The BV is showing correct for me in the current build. The cost is still around 2.4 million which is a bit too low. Its odd because there doesn't seem to be anything particularly unusual equipment wise about that Ontos. I checked on a few others and it doesnt seem unusual to be off by a few hundred K. So this needs more investigating.