As with all repairs, it would depend on what is wrong. If the LED is broken, you can probably just replace it. If the PCB trace is broken, you can repair it (though it will be more difficult). If the controller is bad: it would be easier to get a new keyboard.
I can't comment on the price, but I use lots of keyboards without any lock indicator lights at all (IBM 1390120 for example) and they work fine for me. You could buy it, and not fix it and still be happy.