I did the same, gotta keep an eye out for good deals. Last year i got a 18tb ultrastar HDD for $40 cad from an auction ($10+$30 shippibg to RMA)

Also shucked a 12tb Ultrastar out of a external enclosure

At one point I got 3 used 1tb drives for free out of an old business server

Im up to about 40tb of storage across all my drives now