Seagate have an Exos M in 36TB for about £450, so 24 of those could do it. Three vdevs with one parity drive each? Call the project £13k? Not exactly a product

Seagate have an Exos M in 36TB for about £450, so 24 of those could do it. Three vdevs with one parity drive each? Call the project £13k? Not exactly a production grade setup, but it'd do the job and you'll see fewer failures each year than in 544 10k SAS drives.