The vast majority of my rifle shooting uses cast bullets, so my out-of-pocket costs are much less than if I use commercial jacketed bullets.
I routinely shoot TEN-round groups, finding that they give me a more-precise reading on how the rifle and load are truly performing. Even five-round groups can easily mislead us.
Some years ago, a writer questioned the ballisticians from quite a few bullet-makers such as Sierra, Speer and others, asking what they thought was the MINIMUM number of rounds-per-group required for an honest evaluation of a load's accuracy. After much hemming, hawing, and beating around the bush, it all cooked down to these ballisticians' collective opinion that seven rounds was the minimum number of rounds-per-group for a valid determination of comparative accuracy.
If the rifle ROUTINELY shoots tiny 3-shot groups, that's wonderful. My Savage .338 gave me three consecutive 3-shotters under 3/4" from 100 yards (two groups were under 1/2"), with three slightly-different charges of RE-19 powder. Since I was shooting the 75-cents-per-bullet Barnes TSX, I immediately declared my "load development" to be over, zeroed the rifle, and went hunting. In over forty years of handloading, this was the ONLY time I was this fortunate.