I make some purchases at West Marine for the convience of it.
When I have time and the energy to search for stuff to try and save some bucks I will, but in a bind and short on time, West is usually a whole lot easier.
The OP found the price they wanted after searching, but had made the purchase prior at West because they had it and it was convient. Your paying the extra dollars for the convienince of having it on hand, in stock, readily available, no shipping, and easy access with hundreds of stores all across the country; usually minutes away from most major ports.
The other side of this, the
seats you find at your typical hardware store are not going to fit on your marine head. Same material yes, differnt size made for the marine market means the are produced in much smaller quantities. The runs form the manufacturer on your household seat is probably in excess of thousands a day. The run on the seat for a marine head is probaly around 1000 every 5 years.
My example is just a guess, but I think you understand what I am trying to say. It make a huge differnece in manufacturing cost when you are only producing 1/1000th of what the other guys are.