I think it is quite likely they want to get a base price for all their models below $1,000. There is something psychological about the $1K barrier and it would stand out to see one model on the keynote slide priced at $1,099.So does that mean that the rumored iPhone X (or whatever they're going to call it) Plus is going to begin at $999?
I'm betting they keep the same 64GB base memory too in an effort to get the iPhone X Plus to $999 while driving customers to pony up the extra $150 to get the 256GB storage. I still don't understand why they don't have a 128GB option for $50 more other than milking unnecessary costs from their customers.