ShowerGard must be a trademark as it's not a generic term. There are some treatments that can be applied to glass at the factory that chemically change the outer surface. Basically, they bond a layer of material to it so that the microscopic irregularities of the glass are smoothed out. SOrt of like waxing your car, but applied so it becomes part of the glass and doesn't wear out like wax would. It makes it easier to keep the glass clean as the water beads up and flows off, so mineral deposits and soap scum find it hard to stick. A couple I've seen cost around $7-10 per square foot, so that does add up if you've got a lot of glass surface in the doors/walls. Now, is it worth it? Depends. A properly built shower for $6K isn't out of line, but it depends on the area you live in and the materials chosen.
Check out www.johnbridge.com for an education on building a shower...it's a similar forum that specializes in tiling, where showers are a major component.