I've bought from a lot of different vendors too. . . . I have also bought a few things from OPGI but find their prices can be up to 3 times the cost that others charge. OPGI does have a few parts that others don't carry though.
I also consider OPGI to average on the high side, but in looking back, I see I've bought more parts from them than anyone else. Maybe they've had the best selection at the time -- or availability. It pays to compare prices. I'm in the market for the upper and lower tailgate moldings, plus two sets of tailgate extension moldings for a '68 El Camino. As of today for all: OPGI $111.97; GU $145.91; NPD $168.90. However, I also need a set of lower side body moldings: GU $119.95; OPGI $ 249.99; NPD $279.95; so OPGI wasn't low for all my immediate needs.
You can enter OPGI part number into Summit Search Engine and buy the same part (from OPGI) at a cheaper price and free shipping if it's over $99. I found out cause I was looking for door handles and some other trim parts, saved couple of hundred by buying the same OPGI parts through Summit.
I never knew that. Very good to know and an example of why TC is great. So, I just tried it. RE the '68 El Camino above, a pair of tail gate extensions from OPGI are $20.99. The duplicate extensions thru Summit at $19.99. Good deal! But, the pair of upper and main main moldings that are $69.99 at OPGI are $79.99 at Summit. Again, it pays to shop around.
I appreciate the comments from Rick at NPD. Good to know that some are trying to inject quality into the mix. And, the comments from NickeyChevelle, 658Chevy and Billdini about customer service are important if you're looking for more than a one shot deal.