Re: Why are seed potatoes so expensive now?
Watch out for late blight; it can be seed borne, and will wipe out your potatoes, your tomatoes, and all of your neighbors' potatoes and tomatoes too.
A sharp increase in price may be due to serious late blight problems in much of the country a couple of years ago; though I would be astonished at a price of $1.00 / lb in farm quantities for conventionally (not organic) grown potatoes. The Fedco catalog was listing conventional potatoes in 50 lb bags for $20 to $31; of course for most people that's plus shipping, but that's just the first listing I grabbed. Organically grown seed potatoes do run higher. Varieties for which the demand is greater than the supply may also be more expensive.
Supermarket potatoes may be carrying quite an assortment of diseases, and in addition may have been treated with sprout inhibitors. Potatoes saved from your own crop may be OK, but keep a really careful eye for disease problems, both the year you grew them in and while they're in storage; don't plant them if you suspect disease, and, for the sake of all your neighbors, don't plant them if you had any late blight in the field.