I spotted a pretty nifty little mechanic in a recent session of Chgowiz's OSRIC/1e game last weekend. I'm playing a thief, and I mentioned to the DM that I'd like to run a few errands around town between sessions. No need roleplay it all out, especially since we're trying to run a wilderness sandbox setup that focuses on getting the players out the door and into the wilds.
So we just talked over what I wanted to buy (a new sling for starters; my old one had gone sailing off into the forest when I rolled a critical failure vs. some goblins). Then he rolled randomly to see how many days elapsed between sessions (3 days). He ruled that each member of the party would spend X gold in those three days, either on supplies or food or lodging or what-have-you.
The idea of charging players hard money for every day they tarry in town struck me as a really neat, concise way of keeping up the pressure to explore in a sandbox setting. Sure, towns are extremely safe and a good source of supplies, but characters in a sandbox game shouldn't get too comfortable. It's a cinch to charge 'em a few gold for the material comforts of a town. The key is to make sure the gold isn't spent idly; GMs should offer up new rumors, improved reactions from NPCs, or even interesting material goods. Then the players don't feel like they're getting cheated out of their gold -- but they do feel the pressure to get out and explore to find more.