Well, it's not April 1 yet so, seriously? Each?
Well, their business(es) are complete cars, so high seat prices keep them from becoming seat manufacturers.
A couple of these (in 15", 16", 17" or 18" widths):
Kirkey 41V Series Aluminum Vintage Class Bucket Seats - Free Shipping on Orders Over $99 at Summit Racing
...and a couple of these:
Search Results for kirkey vintage Bucket Seat cover - Free Shipping on Orders Over $99 at Summit Racing
...and you're covered with 2 seats for less than $650.
You'll need some seat rails, unless you're taller than 6' and want to bolt the seats to the floor.
Seems to me that Kirkey supplies a nice product which is relatively inexpensive.
If you have your own seat brackets fabricated, you can modify as necessary for seat height AND for back rake (degree laid back).
I think the pricing signal from SPF and ERA is pretty clear. They don't want to sell individual seats.
DD