The main difference between Battletech and say Traveller is the scarcity of interstellar transport. In Traveller little tramp trader ships with ability to jump are common enough for a little group of players to have (on a mortgage). In Battletech, you have to be fabulously wealthy to buy a Jumpship, or basically indenture yourself and your descendants to some House or corporation.
There is also a discrepancy in Battletech between the goods you can buy with c-bills and want to buy with c-bills.
There is one other option and its an option that is also used by mechwarriors to have a mech and that's hereditary. There are Roma in the Free Worlds League that have these ancient jumpships that they keep going. Dropships are the same way. A lot of the hardware has been around since the Star League.
So it's kind of, "Start your own mortage.", "Be part of a giant Corporation", "Be a spacer family." or, "Your uncle with no relatives died. His Dropship/Jumpship is yours now."
I would say if it is a merc campaign then it is about expanding your merc unit. If it is a House campaign, then theoretically costs do not matter since you are working for a House, meaning effectively unlimited monetary budget and it becomes more an issue of quartermaster priority.
The reason the big jump in costs noted above exists compared to Shadowrun for example is because in Battletech, characters are dealing in military hardware. How many private individuals today can realistically expect to purchase and maintain a Main Battle Tank on their own?
Yes. The jumps are because you are buying military equipment. But it leads to two different income scales. Either you have no income and you're struggling to get the equipment that is cheap to start out with. Or you had an income and you are struggling to be able to pay for the military hardware.
Shadowrun uses things like Tech Levels to keep the scale up. You start with enough money to get level Blah Wired Reflexes.
Dungeons and Dragons use magical levels to keep the scale up. You start with a long sword. You end up with a longsword +5.
Technically Battletech has a sort of military scaling. You Start with a Commando. You end with a Hellstar.
But there is no kind of scaling for the lower parts of the game.
If you are a solo MechWarrior you're hoping to get enough money for replacement parts with a little extra. When you're a Mercenary outfit you're hoping for enough money to replace your losses with a little extra.
Clan or House units are outside of the "Need Money" scale, except for scale one. Maybe you want enough money to buy a sniper rifle. Maybe.
But Clan or House unit games are by nature more Space Opera games where Mercenary games go back to Military Scale oriented. But that's outside of character progression. It's a unit progression.
Solaris VII supports a single MechWarrior scale of progression. You should eventually be able to either swap out your Warhammer for a Mad Cat. OR. Make it into a Warhammer +5 with ferrolamellar. etc.