How much RAM does a single BL server use up? That VPS server for $15/mo has 1GB of RAM, and I heard that BL servers only take up around 100mb to 250mb? (Not sure)
On average a server with less then 20K bricks and less then 10 players will use no more than 250-300MB. If you get more then that, say 25-30 players with 50K bricks, the process will use closer to 450-600MB. If you run a server with a lot of vehicles, add-ons or events, the memory usage goes up even more, Kong's Deathrace is using 414MB with only 14 players and 23K bricks currently.
But, the only time it will use up to the max of 1.67GB is if you're running a full 99 player server with a lot of events or add-ons. Raven's FT with 60 players used about 1GB and Filipe's Steam server with 99 players used about 1.3GB, but he was running pretty much all default stuff, so that helped keep the memory usage down. Just some examples of servers I've observed.