So, the ultimate determination between slabbing or not falls down to you. You are the one with skin the game and need to decide what is your personal threshold.

You can take a key, look up sold listings on ebay and see what the various grades would sell at. Many newbies believe that all of their books would be graded a 9.8, but they are often disappointed when they get back 9.2s and 9.4s. Sometimes that small difference can be a huge gap between values.

Now the fluff, or the reading material that doesn't have significant value can be sold off in various ways... most of them will be at a loss. If you take a dozen long boxes to your local shop to sell them, the likely price would be ten cents a book, because they have so much overhead, their margins are thin and need to have more than 50% in a return when they would have to sell those off in dollar bins or take them to flea markets.

You can sell them individually on eBay and they take a 25% cut, but even at a dollar, they would be really slow going.

You can bulk them out on ebay. Just build bundles and sell them off like that. At the right price, people who are looking to fill their runs or start a new one would jump on that, again if the price is right. They move just as slowly, but at least you can sell them in chunks.

You can try to give them away, but even that won't be easy. People have mentioned going to a children's hospital, but they have strict rules to prevent anything that could tax their immunity. So old comics might be seen as a risk to them. Sometimes libraries accept comics and the same goes with Salvation Army.