$4.90 and $7, respectively. I have compared 10+ 3 prong plugs and the all are essentially the exact the same. As for the IEC's. if you look inside them, the P&S 4300 makes 7x more contact per male blade than any other IEC. Most "pinch" the male IEC prongs between tweezer-like connectors (approx. 1mm x 2mm area per side), Schurter's has flat blades that make contact along the full side of the prong (2mm x 7mm per side), so mechanically they are superior.
The Marincos are excellent, but when I compared them to the forementioned, I just could not justify paying 350% more, besides their IEC still makes 1/7th the contact of Schurter's.
By the way, Marinco makes Watt Gates plugs and IEC's, that's why they look indentical externally. Although, WG gold-plate their more expensive units and have modified the wire locking and blade contact mechanism inside.
PS. I suggest that your replace your wall outlet while you are at it, it makes a noticable difference in backgound noise (it least it did in mine). I suggest the Pass & Seymour 5242 duplex outlet ($2.90), it has a Pit Bull like grip 5 times the normal outlet.
Pass & Seymour components can be found at any major electrical vendor, especially those that cater to contractors and electricians (except the 3 Home Depots near my house). Just call a few in your yellow pages.
The Schurter IEC's can be ordered from www.alliedelec.com