Value on a motorhead tuned hw50s

I've seen Paul Watts tuned rifles bring a premium with proper documentation. But his tunes are more involved, and include machine work, and cost more with a longer wait time. 

Aside from that, I wouldn't expect a tune to add very much at all to the price. At least not more than the cost of a drop in kit, and likely not that much. 

So "it depends". And a lot of it depends on what it means to an individual buyer. 

Just my take.