If you expect to be successful you have to use the same loads in practice that you will use in the field but I do think you can substitute a bullet that isn't a premium bullet for practice.
If your premium bullet has already proven itself & you know that it works I see no problem subbing in something cheaper if you're busting rocks or punching paper.
If you are forming cases it's much cheaper to just use a cup & core bullet, actually you can do it with out a bullet although the shoulder will be just slightly rounded. Many fire form loads are very accurate.

Dick