Long campain, russian, after first mission:
Unit cost for change core unit (KV1 m1940) is not the same as for the same unit in the expand formation. But actual cost used during change is not shown in the "change", but shown in the expand formation.
The costs to change tend to be lower....You get sort of a trade-in on the old vehicle. Also you are paying for the vehicle while the crew transfers in to the vehicle. When you expand you have to pay the full price for the vehicle and the new crew. The advantage of changing is that you get to keep an experienced crew