@Hudson5432, You got the right numbers - the methodology is a little off.... Generally, your numbers are correct, but the TCA listings in the Modern Lionel 1970-Present category of the interchange generally omits the "6-" prefix. (the 8- prefix is for large scale trains). As such, with your limited set of items, it is not hard and fast that the interchange would have a record. Your best bet it to look at soled eBay listings using the Lionel numbers as a starting point.
( NOTE: links to ebay were removed per our TOS!)