You can take a sub-$1000 benchtop mill (Sieg X2 or X3, for example), add less than $1000 of new parts and less than $1000 worth of motors and electronics, and have a benchtop CNC mill capable of working with aluminum and brass with no problems, and with steel in light passes.

If you don't want to do it yourself, you can buy complete from-the-factory benchtop CNC mills (Little Machine Shop: $4500, Tormach: $6k-$8k). If you don't need the size, you can get desktop CNC mills, "ready to run" for about the same price as doing it yourself (Sherline: $2k-$3k).