Like it or not, ebay and auction sites like it are part of the real world... idiots are there for sure but not everyone is.
If you have a bench vise, I recommend using it for cracking coins. For ANACS, PCGS, and NGC holders- Place the holdered coin in a plastic baggie (to keep the coin or a piece of plastic from escaping) Place the bagged slab into a vise (2” edge-wise). Squeeze the vise until the slab's plastic seam begins to break (you will normally hear & feel a "pop"). Rotate the slab 90-degrees (4” edge-wise) & repeat the vise squeeze. (You will probably again hear a "pop"). Repeat as necessary for the slab to come apart. The seams normally break on 3 or 4 sides so that the slab opens like a clam shell & the insert can be removed with the coin intact within the insert. You then simply bend the insert and the coin will release without your needing to press/touch the coin's surface. Some holders like the ones from ICG, do not crack open easily. If you are cracking an ICG holder then you can consider using a band saw or plutonium laser.
My wife sold our only plutonium laser at the last garage sale. I knew I'd be needing that thing......
I can only speak for NGC slabs as I have not cracked open a PCGS slab yet. I buy some coins that are "Details" for my own study. To open an NGC, I wrap the slab in a towel and stand it on its long side. A couple of good whacks with a light happer will crack it down the side, then I use a flat screw driver to split it the rest of the way. The center of the slab is a flexible rubber, so there's some give to it. Pretty simple, actually.
The PCGS slabs are a little harder to crack open. I've found the best way is to clamp a vice grip on one of the top corners, and twist until the slab cracks.
I think PCGS slabs are easier to crack. One crack across the middle with tin snips and you have the label one side and coin in the bottom. Then a small screw driver I can run down one side of the coin outside the ring and separate the two pieces. Now I can just pop the coin out of the ring. If it was only that easy - a lot of the ungraded stuff on ebay are problem coins (at least the ones I look at) and some of the graded ones are over priced in my opinion. In a lot of cases if you want graded you are better off buying one already graded. Just my opinion.
For NGC, I've used hammer and tile floor. For PCGS, I've used bolt cutters. Cut right on the "bubble" next to the coin, avoiding the coin inside. It makes a nice, single crack along the face of the bubble that you can just "hinge" open with your hand, and the rubber thingy and coin is just right there. Done that a few times, with no problems. I have only cracked out coins from slabs because many of the coins that I wanted in my albums in BU condition ONLY appeared for sale in slabs, it seems. I hope I won't have to do it any more!
Actually there is a very good reason to free the coin from it's coffin. It's called: (wait for it) Because! (you don't want it in that holder for any reason you choose)
Maybe they should all be in holders, 100% of the set? What's your album worth? You know that the 85% that wasn't in a slab can be the weakness of the entire set, as far as grades are concerned. The 15% in slabs could have added value to your set down the road, especially since you do not know what the other 85% is really graded at. I've seen the guessing games with grades on the forum, it's a crapshoot. It could be nice to have a few respected opinions in your collection. I'm not against cracking slabs. It's just that I do not practice it because they are scarce from my point of view. When I get a coin in a slab and it does not fit my set storage option, I buy a second one unslabbed, to fill the spot. I keep the reputable TPG as is.
^^^^yup that's what I did, bought a second raw coin for the album; a 1896-O barber dime. Didn't have the nerve to crack out the PCGS, can sell as is to get money back.