Helldivers 2
Microtransactions in Helldivers 2 are summarized as...
The game contains a store with a limited amount of cosmetics that rotates a couple of times per week. These cosmetics are purchased using a premium currency, however this currency can be earned in good quantities through regular gameplay as well.
The premium currency comes in bundles that always leave you with a little bit left over. That being said, all cosmetics are relatively cheap compared to other games. Most cosmetics range between 1-3 USD, but since the premium currency can also be earned in-game most cosmetics can be earned for free. You can't realistically earn enough items to buy out the shop every time it rotates, but you just might earn enough for one or two items.
The game contains multiple Battle Passes with a free and a premium track. The premium track can be purchased using the premium currency, which means you can earn it through regular play as well and no purchase is necessary. The battle pass does not expire with time. New battle passes release frequently. At first this was once a month, but this has since slowed down due to quality concerns.
Some items in the Battle Pass are not cosmetic only, they provide different weapons or certain gameplay enhancing items for your team.