While not perfect, the Moto Z is fairly unique in its ability to augment its capabilities via Moto Mods, and you can get started with the handset for $450 unlocked from B&H today, with no sales tax outside of New York and New Jersey.
That’s still not an inexpensive phone, but the $250 you saved can go towards mods like the Hasselblad camera attachment, the Moto Insta-Share projector, or the JBL SoundBoost speaker mod.