After one of the updates (not so long ago) there’s been for a very short time a bug that actually made Stalingrad FA orders earning per XP work as for other campaigns, so you earned x4 more orders in Stalingrad campaign.
Still wonder why bugs like that DEVs can fix in matter of 1 day or even few hours, but some take months or over a year to fix 
i know when i got the mk owen machine gun with just even on top modification just a 30 round, and just 3 refills, i thought what the heck! i literally went through so many weapon orders and dismantling and upgrades to get it!
not to buy campaigns
but say for example the sniper rifle i needed to upgrade to to modifications
i had to upgrade squade abilities
then modifications
then purchase it
then upgrade it
all for one rifle for one soldier
then when i sell it the cash is doesnt even get me an upgrade on the basic sub machine gun that the tanker crew have!
exactly you grind and work your way through it, you finally get something
but that something is just another road, for you to grind/ pay/work your way up to finally get something
which in itself, then needs work on
everything is just constant paying, griding, leveling
they cant let you just enjoy a game
THe price of a AAA game for a premium squad litterally useless most of time … kinda sounds like bullshitiest F2P ever for me
its the full price of an AAA game to max one soldier and weapon
thats just for one soldier from one unit from one campaign