The best price might not be the best deal since this one will be done twice.

This is example of low price and or limited knowledge of the contractor. Since having Hardie Backer or cement board directly screwed to your waterproof membrane (hotmop or 40mil shower pan liner) is a recipe for a water leak and water damage and how much damage depends on when you find it.   Most likely when you find the damage; the contractor will be long gone because they will not be in business for long by installing faulty shower pans.     Go with the experience of Roma Tile Ltd. We have been getting projects done right the first time since 1964.