My first Gore-Tex garment was a Mountain Jacket from Berghaus. I still have it and it cost around $500, twenty years ago.
That jacket is a two-layer cloth. The latest garments from Klim and Aerostich are triple-layer. The cloth is extremely expensive, even wholesale, hence the prices. If they could make it substantially cheaper, all the major manufacturers would have it in their line-ups.
It's the best that is currently available, and priced to match. Depending on your type of riding, other gear might be perfectly appropriate and much better value for money. But if you want to keep out the water, in extreme conditions, there is no substitute.
For ultimate protection and flexibility, I recommend a two-piece suit with a 3/4 length jacket. Personally I stay away from the one-piece suit, but ymmv.