3000 roubels

The number 3000 roubles comes up consistently throughout the novel. It seems like it's the only money ever dealt with. I can think of four examples off hand having to do with 3000 roubels.

The number revolves a lot around Grushenka. It's the amount of money that Fyodor set aside to pay Grushenka for visiting him at his house. It's also the amount of money that Dmitry spent on Grushenka when they went out on the town. Dmitry got this money from stealing the money that Katya gave him to give to her aunt in Moscow. So now it's the amount of money that Dmitry owes Katya.

We also find out in this chapter it is the amount of money exactly that Fyodor still owes Dmitry. Although before Fyodor told us earlier that Dmitry actually owed Fyodor money, I guess Dmitry found out some information.