Yep, that is my one complaint, as well. The ratio of spending money to offshore money is ridiculous. It will take way, way too long to work your way through the weapon unlock system.
What is worse are the facts that:
Weapons upgrades aren't just a matter of preference, some are demonstrably better than others and required for harder difficulty.
There's significantly more weapons than slots you can equip them in, when you put a weapon into one of your slots you have to "buy" it, which means cycling out weapons + all the attachments costs an absolute fortune (many in game hours of work)
The different classes are better suited to different weapons as they get specific bonuses with them, if you spec into one class and give yourself a tuned loadout. But your loadout isn't specific to the class you're playing you just have a fixed inventory size to accommodate all classes, so if you hop between various classes you'll need to get rid of some of your guns and then buy the same guns again, buy all the attachments again.
In game in any other difficulty that easiest, requires you to work as a team in the same kind of respect an MMO dungeon does, there's not enough skill points for everyone to be good at everything needed for the missions, so you ideally take 1 of each class and support each other.
Except if everyone is spec'd in one class, and swapping classes is expensive, people can't just do it easily on the fly, there's no saving of class configurations or inventory loadout, which means that you have to fuck about re-specing your entire character, potentially just for one game.
You can't respec ANY of this from the lobby.
The unlocks you get are random, if you're a ghost and you want to spec silencers and attachments that decrease visibility of weapons, guess what you better get lucky and roll a 1 on a D500 dice otherwise you're screwed.
The cost of everything is at least 2x more expensive than it should be.
The entire system is a complete joke, whoever thought it up is an idiot, there's simply no polite way to say that.