I think the price difference between RP and Winchester vs. Lapua is highly overstated.
Yes, the pricetag on Lapua is essentially twice that of RP/Win, but relative to the actual costs of using that brass, it's a drop in the bucket.
I only "lose" brass at tactical matches, or when it wears out.
Wearing out: When working with a new rifle I'll usually end up wasting a couple pieces of brass from loose primer pockets after repeated firings - finding the load that produces the best accuracy at the best velocity whilst still providing for repeated reloads. So, of those 10pcs wasted, the difference between having wasted RP/Win instead of Lapua is ~$5. Hardly worth crying over.
Let's forget about the fact that Lapua will outlast RP/Win (assuming moderate/safe pressures), and just assume any of these headstamps will last ~10 firings, which is entirely reasonable.
250-300pcs is enough to wear out a 260. Over the course of those ~3000 rounds or so, you'll have spent ~$400 on powder, $100 on primers, nearly $1000 on bullets, and of course $300-1000 on the barrel/gunsmithing itself, to say nothing of the expenses of gunclub memberships, fuel to get to/from the range, match fees etc etc etc.
The price difference between Lapua and RP/Win is ~$150 for those ~300pcs of brass.
So after spending thousands of dollars in stuff so you could play/train and shoot out a 260 barrel, you're going to quibble about $150 extra on brass? To say nothing of the fact it's "higher quality" brass that you're probably getting some additional service from....
Losing brass: The price hit here sucks more than it does for wearing out brass, but it's still not that big a deal. You basically only "lose" brass from shooting at tactical matches. Plus, you don't honestly lost that much. I think most match shooters would agree they don't lose more than 25% of their brass on average, if they at least give their brass search "the old college try". To recover 75% of your brass, you don't have to be "that guy".
So, you go to a match, fire 200 rounds and lose 50pcs. It just cost you $25 extra to lose new Lapua instead of new RP/Win. That's $25 on top of the ~$250 match fee, the $250 you spent on lodging, the $200 you spent on fuel to get to/from the match, and on and on and on.
Losing your precious brass sucks, yes. But in what is an expensive hobby/past time, I just don't think using readily available Lapua is that big of a deal.