Is the price a bit high for an R10, even in great shape?
You can say that again. When appraising a Darne R model, START WITH THE TRIGGERS! There are some that simply can't be made better, and if you find a good one that has decent triggers, it is worth more money. While a great fuss is typically made about chambers, a Darne will always have plenty of material in that area of it's barrels, and lengthening them on a hunting implement like an R10 isn't a huge deal. I run the Winchester low noise 2 3/4" loads in my 65mm chamber Halifax with no problems, another option to consider.
Or, you could just buy the right ammunition. S vous plais.
Nice as it is, I'd hate to be into that R10 for more than $1500-$1800 or so. Assuming good triggers.
Best,
Ted