I think UMB, by looking at different whitepapers, seems to be less expensive than LTE, because mainly of the lower latency, greater spectrum efficiency, and can be used in many spectrum bands and spectrum carriers. On the other side, LTE also has the similar spectrum efficiency and will reduce cost per bit.

UMB; DL up to 290mb/s. UP; up to 79mb/s. low latency of 17ms.

LTE; DL up to 150mb/s. UP; up to 50mb/s.

I think UMB is actually better than LTE in many areas.