Also, I find it hard to reconcile this logic with MDD's peregrinations. She basically said (or strongly implied) that the horse's life was what was needed (wasn't so clear on what would be the payoff). Later, she said that Dani "knew" the price. How could she? You said all that you needed was a horse, and I'm supposed to assume that you're going to kill my baby? For me, that interpretation just didn't make any sense. So, I assumed the "price" in question was the half-life vegetative state that Drogo wound up in. The way I read it, you couldn't have "purchased" real life for Drogo with a horse or a baby...
As far as the stillbirth, I guess the fact that it came out looking like a dragon was more eye-popping to me--I just couldn't imagine that happening without it being signficant. It's one thing to say, "Your baby was born dead," but quite another to say, "You're baby was born a dead, winged lizard." Unless we were led to believe that this was common for Targaryans, it strikes me as a pretty singular event. [Bill Cosby version: "My darling, I love you very much. You've just given birth to...a lizard."]
All this being said, I absolutely DO agree that your interpretation fits better with the way they portrayed these events in the TV show. Everyone saw MDD cut her eyes at Dani's belly, and the whole thing seemed staged to portray MDD as a big fat vengeful liar. Which leaves the birth of the dragons as just a very strange, miraculous thing that happened without any obvious cause, other than Dani's desire for dragons.
For me, that's less satisfying. Magic is magic, but I like to feel that there exist some underlying "rules" that explain what's happening. If bringing Drogo back from the edge of death by sepsis would be a big damn deal, then how much bigger of a deal is to bring back dragon eggs that have been dead long enough to have fossilized? And what price was paid? As you mentioned, the explanation of the rules could be forthcoming later, but my suspicion is that this will remain a headscratcher.