I think it all depends on what the selection is and how many you're willing to buy. The $19.99 price point does look absurd at first, but you can get down close to an item price that matches other retail IF you capture all the deals and buy at the multiples/price thresholds needed. Their strategy is to make you feel like you're saving a lot of money, while getting you to increase your total basket purchase and make a return visit. it's similar to what KB Toys used to do. They would have price tags that Showed $8 for a $5 figure, then a red slash showing it as on sale at two for $10!
The current offer @ Kohl's is 25% off everything and $10 in Kohl's cash for every $50 spent. If you bought one figure, you'd pay $14.99 vs. $12.99 at someplace like Target. Not terrible if you find something you really want. If you bought four figures, you'd essentially pay $49.97 (including the $10 Kohl's cash), so that's like paying $12.49 versus $12.99 elsewhere assuming you come back to spend the Kohl's cash on something else. Feels like a slightly better deal, but you don't really get the $10 off - just $10 towards a future purchase. If you can stack a 15% off personal rewards coupon with the other items, then it starts to make more sense.
Compare that to buying a case at someplace like EE. They have a case of 8 armor up figures for $109, so now you're paying $13.75 per figure - more if you can't get the free shipping.