You may have read our report on the rumours presented by VG247 yesterday, a rumour that said Bungie would start to charge real money for ammo packs in Destiny. This has now been denied by Activision who says "We're not doing that".
There you have it, the ammo packs will not be on sale for real money. We're of course curious about VG247's source in this case since he or she was supposed to be "familiar with the matter", but hopefully the source was just plain wrong. It would be strange if Activision were weighing all their options on how to monetise Destiny, but it would seem that at least for now this isn't a direction they're going in.