The price of a 405-2 is around $400 here "serviced". The service is always questionable until you open it up and see what they consider serviced.
I actually think they are really good amps for my type of listening, but they generally need some work. I have had quite a few of them over the years but I think the price/performance doesn't really even out.
The Chinese boards cost $50. Another $75 if you want the case with all of the modern connections already cut out. You can do a lot to improve it for the extra $275 that would have went towards a real 405 that needs work.