I used to do them nonstop, and the most common was a bunch of runes, a rune item or two, then maybe some ores or bars. You are basically guaranteed a rune item, so worst case was usual around 50k for me. I probably did some number in the hundreds, but my best drop was only like a zammy plate, which was something like 1.5m at the time. God pages weren't too uncommon which was cool, along with that ugly trimmed (t4) or something I can't remember. Anyway, I really wanted 3rd age, but don't regret it. Treasure Trails are really fun for me, I love killing things to get them (I killed Jellies mostly, great experience!) and I love solving the clues. You are guaranteed a reward, so while it's disappointing getting no really valuable items, it's worth the time. I look forward to hearing other people's experiences.