It is nice (a bit pricier) to have a "plug and play" kit and props on the design, but a Biltwell 4130 chromo made in USA hinge is only $44-50...add their finished vinyl covered seat pan and you're still only at $175 with the hard parts taken care of.

Not trying to be cheeky, I dig BC and shop there, but comparing like quality products raises an eyebrow.

Now a full finished kit WITH seat and springs for $275ish...that would open some wallets I bet. Maybe offer a leather option at a premium.