RE: 12 ga. sabot slugs
Unfortunately that is the down side to the new slug technology from what I can see. All of the saboted slugs I have seen are around 10 bucks and up for 5 shells. A bit extreme in my opinion.
You could probably shoot non saboted slugs if you wanted to, mine seems to like them. They are a lot cheaper. However they foul up your barrel something awful and like said above, the ballistics are not that impressive in most cases. Nor is the performance compared to a premium saboted slug bullet.
I got the whinchester 400 grn 1700 fps platinum tips for 10 bucks at walmart.
You pretty much have to find what works good in your gun and then buy a few boxes of it to sight in and practice with. It can get expensive and time consuming if you don't have a lot of money up front.
However once you get it set up it shouldn't be that big of a deal unless you shoot it alot. A couple of boxes a year should suffice. I would think Maybe another box now and then to practice with. These really are not guns you go plink with. I may try taking a woodchuck with one though.
Good luck,
Paul