All Topps baseball cards from 1995 onward have the given odds on the back of the packs.
Since buying packs of baseball cards are almost essentially gambling, I suppose it's nice of them to give you your odds of 'winning' your prize. I'll be using the odds from 2012 Topps series 2 for this here post.
Introduced in series 1 back earlier in the year, series 2 had these inserts as well:
The Golden Moments inserts. Drab to look at due to them being made especially for the autos and relics. These fall 1 in 4 packs.
Speaking of the autos, the Golden Moments autos will run about 1 in 335 packs. Those are tough odds but usually your auto from series 2 comes on one of these cards more often than not. Chad here is from series 1 but I had no other auto to show from this insert set.
Or do I? this MONSTER hit came from a pack at the local shop last night. I was quite stunned to find such greatness in a basic flagship Topps pack. This is numbered 08/10 and the foil parallels fall at a whopping 1 in 11,800 packs. Now those are some tough odds and have to be the absolute biggest pull odds-wise for me. Garvey isn't in the Hall but perhaps he should be.
Normally when buying packs you don't beat the odds but I think it's safe to say even after buying 8 packs, I demolished them.