Fitting an upstairs bathroom -cost? Saniflo?

We once stayed in a B&B in France and the en suite bathroom had a saniflow type system. We were quite embarrassed to flush the toilet in the night, because of the noise it made and thinking we'd be waking the entire house.

Thanks folks for all that info.  It would be in an adjoining room to the bedrooms so noise (from the saniflo not the users) might be an issue to certainly factor in.