Some ten 300 mm diameters and a pair of 660 mm for my big windmill.
It cost me 64 pence per kg, which comes to about £3 per small disk (about $5).
Transport was a bit more expensive going via the galvanizers,
but I think it will be worth it.
Cost per disk:
transport (in total) £7
Total was £20 per galvanized disk delivered to me in a batch.