It's not cause they are overly proud. The system is built with the best materials- stainless Steel and billet aluminum, very expensive materials. Plus you don't have to purchase any clamps with the Trinity system, that's saving there. You don't ever have to worry about the finish degrading, chipping, rusting, etc. Isn't that worth something? When you lay it out it's really not that much. I think you may still be able to get a full set from rocket pig for around 580.00 a set.
You have the best opportunity to see why they cost more. I would run both sets and see what fits you better. From my experience the Trinity's have more top end power. Another thing is the quality is better than the T5's, especially the silencers. The detail and finish is second to none I guarantee you that.
Give us a review when you get the pipes.