There is no issue with rimless or belted rounds in a Ruger #1. Most of the Ruger #1 chamberings develop much higher pressures than the old rimmed British rounds and give no trouble in operation.

No one is suggesting that the cost of the rifle makes it any stronger, the cost of a Farquharson is high because it is an antique, and there are many people wanting to buy, this as always, dictates the selling price, the strength of the Farquharson action is beyond question, with a huge breach block sliding up behind the cartridge it can hardly be anything else, my comments on the unsuitability of the rimless case is really only a comparison, why would anyone want more than a rimmed case can deliver in a single shot rifle ? To chamber it for some modern whiz bang wildcat would be silly, the extractor is another objection to a rimless case, at the range there is no problem, but in Africa, under duress it would be very embarrassing to have your sprung loaded extractor slip over the case rim. There is no need for such cartridges, people have tried to use high pressure cartridges in Africa before, most of them are still there!
And no, our market was not very large, but some of the most important and influential people were using these guns, and it takes a lot to build a reputation, but not a lot to loose it.