Somewhere on this site, you can find a Lee disk volume-weight cross reference table which can be used as a starting point for building your loads. I’ve recently started testing with Vihtavuori 340 which is not listed in that cross-reference, so I’m listing 2 volume-weight reference points for it here.
VN340 is a slow burning handgun powder, which I use for reloading .357M. It’s known for burning clean, being reliable and consistent and for being on the more expensive side. Where I live I pay about 130€/kg for VN340, good old HP38 comes at 99€/kg. Add to this that you typically need more VN340 than HP38, e.g. comparable loads for .230gn 45ACP with VN340 list about 1.2 times the weight of HP38. So if you do the full the price comparison VN340 is about 1.58 times the price of HP38 (again, that’s where I live).