In the Binscape there are 2 types of in-game money. Firstly there is Mulch, which is available to everyone and can be earned continuously through playing Bin Weevils.
Secondly there is Dosh, which is a premium currency. Dosh can be earned periodically by stamping your Bin Card found in your Nest & sometimes you can win Dosh through competition. However, you can also top your Dosh up on the Membership Page.
Both types of money can be used to buy nest items, food, plants, mission hints, a Bin Pet and lots more!