If you can get Spence@greatsantafeproperties.com to do a bath remodel for $50 to $75 a square foot - DO IT!!!! Seriously, that is not a realistic price. He has no idea what he's speaking about.
A bathroom is one of the most expensive rooms in any home. Take a moment and think about it. Tile, faucets, sinks, tubs and/or showers, toilet, plumbing re-work, electrical re-work, etc. The only other room that could be more expensive per square foot is the kitchen.
Have a set of drawings OR at the very least - written specs that you can give to three builders. That way you have everyone bidding on the same thing and no one can say "I didn't include that in my bid".
I wish you well and good luck.