I threw out 12 seeds as a number, and that’s (allegedly) practical for me. That’s about $60 in seed. I’m going to spend a lot more than that on electricity, and if the plant is a runt I’m going to need to buy from a dispensary at >$14/gram, assuming they have what I want.
Even if this is just for your recreational use, I advocate sprouting more seed (of the same strain) than you need, and culling all but the strongest plants over time.