It takes a masterful combination of skill, sweat labor, and concentration to make these. That's why they are not super cheap like the machine glassware you buy in retail stores. You do get what you pay for though, and the value 100% correlates in both real physical quality and that special intangible feeling that comes from something so beautifully human-made.
Crystal vs. Glass
Regular Glass is made primarily from sand. Sometimes minerals are added for color. It is not particularly strong, so it's made thick and heavy to compensate.
Crystal is made with ~75% of the normal glass materials PLUS a minimum ~25% strengthening minerals (lead-oxide, potassium carbonate, and/or silica) to make the material durable. This is the standard upheld within the European Union, which is higher than the rest of the world. The added metallic ingredients in crystal also dramatically increase the ability to refract brilliant light .
The Durability Myth
Crystal's strength is what allows it to be so thin. The myth of them not being dishwasher safe is an old carryover from days gone by when old production methods only used lead additives. Fortunately, our modern glasses are lead-free, and include newer safer materials like titanium. These glasses are tough and will be perfectly fine in the dishwasher - in fact, it's recommended!