The ones the pros use are real expensive
The full version of After Affects is US$999.00
And Discreet Combustion (now called Autodesk Combustion) costs $995.000
IMO those are already expensive.
Getting lightsabers to glow in movies is getting them to glow in thousands of pictures, with the added dificulty that sometimes you need to apply mask frames if, for example, part of your body prevents you from seeing part of the saber.