they are expensive because there are zero corners cut.
your keyboard is your primary interface with your computer and should be a top consideration for where to spend your money in my opinion.
a quality keyboard and peripheral set makes using your system more enjoyable.
a mechanical keyboard will outlast the period of usefulness of a high end graphics card. This makes it a much more appealing investment.
I personally dont understand computing enthusiasts who dont use high quality peripherals.
Preach brother preach. Nothing like the feel of a solid mechanical keyboard to get you through the day!