I have the gut feeling these packages will be sold close to retail price.
Case in point, how much are Star Wars ROTS selling at retail? 9.99 CAN at TRU (from what I saw today). The HasbroToyShop.com site has them listed at 6.99 US or 8.66 CAN. Factor in shipping and you catch the drift. Unlike Star Wars, these packs will be limited as it's for the collector market. So I expect a single pack to cost as just as much as a older 2 pack in retail.
Any ways, I prefer the single packs. I hope there will be less figures released over time as a result.