The astro or g-force gear sets will be around $1200. Plus a clutch and other miscellanious things. It cost me $1600 total to do the Astro gearset in mine with the clutch and everything needed, rebuilding it myself. Yea, it's a lot of money to spend on a t5 but it's been putting up with a lot of abuse for over 10k miles now, and it shifts like butter. We'll really put it to the test next season.
You could do one of the heavier duty t5 gearsets that are rated at 330ft lbs. I believe they can be found for a couple hundred bucks on ebay. Do a 26 spline input shaft while you're at it and a steel bearing retainer. Rebuild it yourself and you'll be under $1k all said and done and it should be pretty rugged.
A lot of people consider T5s garbage but I've seen rebuilt ones take some beating. Nothing is lighter, and no syncro tranny shifts smoother. Syncroed tremecs are dificult to powershift, especially in higher rpm.