While it hasn't been publicly confirmed, I have friends that work at Apple who have already gone through the training for it. They have all stated that the Apple Watch is the entry model at $349, (The one with stainless steel/ sapphire display cover). The sports model is the middle of the road model. I know it should be taken with a grain of salt, but there is no reason as to why I wouldn't believe them.
The watch snobs will tell you that this can't possibly be right, because traditionally a stainless steel watch is perceived to be more valuable than an aluminum watch. I can't say one way or another, but it seems to me that the relative lightness of the Sport version is a feature and consequently could demand a premium.