the OVP is a simple circuit involving a zener diode which is the most expencive part in it, two regular diodes, and a switch if I remember correctly, and of course the changable fuse. All nicely packed in an aluminum case. I took mine apart multiple times to resolder all the joints, not that I was having any problems with it, but here in Canada the dealer wants $250 for parts like this.
I have no idea how you got a fuel pump relay for $28, but it sounds like a good price to me.
1985 190E 2.3L - a constant project.