Static weight (like a saddle) doesn't mean much for tris where you're going a constant speed. You want lighter stuff for bike racing where you're accelerating a lot, but you won't notice a few grams in the saddle for tris. Definitely get something comfortable (i.e., try them out if you can!). I can definitely notice a difference between a $50 saddle, $100 saddle, and $150 saddle, so if the most comfortable one costs $280, I'd say get it. I ride an Arione Tri ($150) and think it's great, but saddles are a very personal thing and you can't be told which one is best for your own butt. Buy on comfort (just be aware that it usually takes several days for your "area" to adjust to a new saddle). Also, make sure that the store measures your sitbones if you don't know what size you are already.

I just got the Fizik Arione Tri 2 Carbon - Braided Carbon saddle - replaced the Arione Tri II - it finally wore down on the nose - some stitching came loose. I like this new seat even better. Only thing was with the braided carbon rails I had to get longer screws to attach it to my seat post, but I had those hanging around, so wasn't an issue. Costly, but it is very comfortable for me.

I love my Specialized Toupe saddle, it's light too, the one I got 143mm = 155g. I got it in April and used it in July for IM Switzerland. Once you have it adjusted just right, it like you don't even not the saddle at all.

Specialized Toupe saddle

They have other road saddles like this with more padding, plus they recently announced the tri specific saddle the Toupe, it's called the Tritip Gel Saddle. The thing with this saddle is that it's in the 280g - 290g range.

Tritip Gel Saddle