Last season Upper Deck decided to pull something from the past (40 years ago) and bring back the NHL logos insert set. Unlike 72-73 they are seed one every three boxes and are a manufactured patch instead of a die-cut punch out. They were very popular with collectors so they brought them back this year along with another 40 year old idea, NHL rings. Here are a few 72-73 OPC logos I picked up at the LCS last year.
If you ever looked at the book value of the 72-73 OPC logos you will find that they are pretty expensive and when you look on eBay you will find indeed sellers want a load of cash for them. One reason is they were only released in the much more rare third series and secondly kids often punched the logos out because they were meant to be used that way. The high value for the set of 30 NHL/WHA books for $1000. While my cards all are tape stained, they are all intact and relatively in good shape (except Bos has a crease and Stl is missing a small piece of the border). They card backs are blank and are listed alphabetically in the Beckett.
Here is one of the WHA ones just for fun.