Are you still following me?
So the next up in terms of price are shaped ones. These often come in 'birth to potty' sets, or are sold as birth to potty types. some are more shaped than others. The most shaped, with elastic at waist and leg i didn't get on with that well, as they were very bulky and took forever to dry. Motherease would be an example of this sort.
The sort I liked best are called One Life. They're a UK company, I think made in Cornwall, and I don't think are organic, which keeps the unit cost down a bit. They aren't elasticated, so dry flat quicker than some other ones. They also come with a pad (as many do) so that when your baby is little they are a bit less bulky.
This sort aren't entirely suitable from birth to potty, as a very small newborn would be swamped by them, and a big toddler wouldn't really fit in them. I think we probably used them from about 12 or 15 pounds, and my two year old still fits them - just. But I've no idea if he's big or not. I imagine he's pretty average.
But there's no shame in using disposables with a new baby anyway! I actually used little shaped ones (that don't seem to be made anymore) for the first few weeks. But I'm a bit obsessive - if you can't tell.
The most expensive in terms of unit cost (although you don't need pants) are all in ones. I think Tots Bots are a brand of this sort. I didn't get on with these at all. They took forever to dry so you need a gazillion. For example, if you use 6 a day and wash every other day, you need at least 12. But if they then take 2 days to dry, you need 24 if you see what i mean. False economy. Also, you don't get the 'belt and braces' aspect of the two layers of nappy and pants.
With separate pants, you only need 3 or 4 pairs with maybe 12 or 15 nappies as they don't need washing so often. If they get a bit of poo on, you can often get away with a swipe of a wet wipe rather than changing them altogether.