Why would anyone assume LCD means raising prices? Good chance stern's cost on a widely used component such as an LCD is less than their cost on a singly used item such as a Dmd. most the costs to stern will be in the initial software rewrite. But this will carry them forward after on other pins. There is no reason to expect an LCD based machine to be more expensive. And stern is not raising prices each pin. The LE type pricing has been somewhat flat over the last few releases. Seems to be some fluctuation on each release probably based on actual costs ( acdc more than transformers, less than xmen, etc).
Finally, why is a backbox LCD important to anyone? You wont be noticing it while playing the game because you will be busy looking down at the playfield. It won't be anything like pinball 2000. If it were located more like cirqus voltaire's Dmd that might be different. But up in the backbox it will have a real minimal impact.