It's easy to put a lot more work and worry into reloading than is practically necessary. The longer the ranges you're shooting at, the more attention needs to be paid, not only to your ammunition, but also to your rifle, optics, fundamentals, ...
Realistically, even a 1-inch group at 100 yards is likely going to fill the freezer at 250. But, you have the opportunity to narrow that if you can, at least as far as your ammunition is concerned.
Yes, 10 rounds per step gets to being an investment, particularly when components aren't cheap or as readily available anymore. That number is based on being able to shoot at least two five-round groups. Over the years, I've found three-round groups to be a mediocre if not poor indicator of consistency and reliability. Many are perfectly happy shooting three-round groups, and that's your option of course. Think of it as your sample size as it's applied statistically. Most of us know when we've thrown a flyer even before we check the target. With three rounds, it's awfully difficult to really measure a group when we're looking at two holes with a third somewhere else on the target.
I generally shoot one five-round group per step on the same day. Measure, chronograph, recording environmentals. Because I live where the conditions are never the same from day-to-day (Wyoming), I'll shoot a second five-round group on a different day under different environmentals. I've found a couple loads that are great for prairie dogs in the summer, but not so great on coyotes in the winter. That rifle now has "summer" and "winter" loads tailored to it.
On the other hand, rifles of which I don't expect such precise accuracy (an elk being larger than a prairie dog) I don't spend as much time on load development. If my .30-06, .300 Wby, .338 WM, or .375 H&H go into an inch at 100 yards, I'm pretty comfortable they'll do the job at 250 as well. 250 yards is a very reasonable number out here.
Put some loads together. See what they do.