If you go genuine gold plate, you will be looking at $150+.

Chrome with mirror polishing will be about $100 since it has an intricate design with lots of grooves/crevices that will need to be polished with a mini buffing tool.

I went the powdercoat option in gunmetal black as it looks more like a real gun. About $50.



I can get the reference number from the powdercoat colour chart if you want to go that way.  

Like you said, painting would be less cost still as a DIY.