More refined and specific search and lower cost of Legendary Sub as well as some other stuff
Change the search engine so it only gives you EXACTLY what you are searching for. Or at the very least, change it so the EXACT search requirements come up first, and after all of them, the "other" options are listed after them, lower on the page.
For example:
If someone searches for "2010 Topps Football", 99.99% of the time, someone just wants the standard football card search, not the chrome or finest, or whatever all of the other Topps set/series options for that year are.
If I wanted "2010 Topps Chrome Football", I would type that into the search engine, and then I would hope ONLY those "Chrome" options would come up, but instead, there are other options mixed in.
So if I just want regular 2010 Topps Football, I literally get EVERY Topps football option for that year when I don't want that.
So by requiring people to type in EXACTLY what they are looking for, it would make things much easier and more organized.
At the very least, do an "Advanced Search" option that we can change to and get those specific and only results for our search.
As for the cost of the different memberships or subscriptions, the Collector Sub is priced very nicely at $59 for the year, but the Legendary Sub is completely out of control at $499 for a year. Taking into consideration that most serious collectors or Card Selling Professionals have multiple memberships/subscriptions to several other websites (because the more "opinions" and data that is available is the best approach), you might find an increase in your "pay subscription" numbers. $299 a year would be more in line with a subscription to what you are offering for the services. You could even cut out a few services that are rarely used.
I personally pay for 5 different memberships/subscriptions at 5 other websites. I only use the "Free" option here as the Collector Sub doesn't offer what I need, and the Legendary Sub, I feel, is simply too expensive, and I don't require many of the additional services in that Sub, and need a few that aren't available.
However, I do use this site quite often for "quick" searches when I'm just curious about something.
Another option would be to add additional info regarding the various "Sets" available from the manufacturers for each year, and where a player's certain card can be found. An example of this would be if I wanted to know what cards are available for a certain player and what packages/sets those cards are in.
Say, for instance, if I wanted to know what Aaron Judge cards are available in the 2017 Topps Series 1, Series 2, and Update. Well, if I type in 2017 Topps Baseball Update Aaron Judge, it will let me know MOST of the cards available, but for some reason, NOT ALL of the cards available in the 2017 Topps Update.
More specifically, if I type in 2017 Topps Baseball Aaron Judge, it will literally list a Gazzilion options for EVERY Topps set that year whether I want them or not (this ties into what I wrote earlier about having a more specific search engine), but it also doesn't tell me what cards for Aaron Judge could be found in the 2017 Topps Series 1 or Series 2. Yes, the card numbers will sometimes help, but if they are an "insert" card number, which is usually just Letters and not Numbers, it won't.
If this is too much of an undertaking, you could always have an easy and visibly noticeable link to a "Discussion Page" regarding that specific set/series of cards and just allow your members to fill in that information.
While your search engine could be judged as "Adequate", it could be much better, and also give your site an advantage that many other sites don't have, and also put you on more of an equal footing with the other sites that do have this function/option.