The whole "just buy 9 Atlases" argument runs into the problem that you don't have that many Mechwarriors. If you have 100 Mechwarriors and resources for 500 Atlases, you can't buy and field 500 Atlases and you shouldn't buy 100 Atlases; you buy 50 Atlases and 50 Savage Wolfs.
There's absolutely no way a single 75 ton mech involves more resources to build than 5 1,900 ton DropShips. No way.
Sensational example, but not quite. Little Boy weighed 4.5 metric tons. A Tallboy bomb weighed 5.5 metric tons. Guess which one was more resource-intensive. A little more relatable: the price of an iPhone 1 is $200. The price of an iPhone 7 now is $650. But what dyou think would be the cost of an iPhone-like device in 1990? Literally priceless, if such a device existed.
The weight of the Savage Wolf vs the weight of 5 Dropships has nothing to do with cost. In fact miniaturisation increases cost, not the other way round. You're using rare and exotic materials, advanced manufacturing techniques, and possibly have lots of wastage, like with RL precision ammunition, and all that does increase material cost significantly.
Then again, as we all know, C-bills and costing is borked, so let it lie. Just think of it as a "unit of measurement" rather than an actual currency amounting to a fixed quantity of goods and services. There's nothing really wrong with balancing campaign games with C-bills if the GM controls for other factors such as availability, BV, etc.