When is it worth going to court?

[Mark Douglas]

I've got a tenant that moved out 3 days after their lease ended.  There are some damages, amounting to around $600, plus a fee of $250 for not leaving the property till day 3.  ($100/day, and $50 for a half day.)  All in all, they're looking at $850.  I sent them a letter notifying them of the damages found, and that the damages would be deducted from their deposit, and they'd owe the $250 charge.  Now they're wanting They were wanting to go to court over my keeping their $500 deposit, and charging them for not moving out when their lease ended.  

I ended up just doing a "cash for keys" deal (in writing), to return half of their deposit, and call it a day.  

Was I right?  I don't know how much it would cost to go to court, but I'm thinking a lot more than $850.  I'd hate to end up losing the case for some negligence on my part.

Is there a certain dollar amount when it becomes worth it to sue the tenant?