Question: For example, 4 4tb drives versus 2 8tb drives. I couldn’t find any info about what size of hard drive (all other factors being equal: manufacturer, type, brand etc) has the most value in terms of price to storage capacity ratio. Or are hard drives meticulously priced to maintain the same ratio regardless of drive size? Sorry if this is a stupid question.

Answer:you can use www.skinflint.co.uk for this
sort it by”Price (per TB)”

e.g. https://skinflint.co.uk/?cat=hde7s&sort=r#productlist

usually the price per TB gets lower, while looking at higher capacities (within the same HDD brand and model)