This may not be too popular based on most of the bulk of the responses I see. However, here is my firsthand experience as a BIG Rigby fan:
I have a few of the California made Rigby rifles and
several British Rigby rifles. I would say that I prefer the British made rifles by a long stretch, of course. However, I have not found the american made guns (at least those that I have) to be bad guns. In fact these that I have are very well made, nicely engraved with beuatiful wood and good shooters. One of mine is a very nice boxlock in 500 NE. It is well built, very handsome, and balances and shoots great.
Now, should the be worth as much as my British born Rigbys? No! However, they didn't cost nearly as much either (My prewar Rigby double cost 3x what the 500 NE boxlock cost me, and appropriately so). Thus, take them for what they are. A nicely engraved and handsome rifle (considering their doubles an upgraded Merkel is probably fair).
Just my $0.02 based on my experience. Take it for what it is worth...