Sigma 24-85 is more expensive than Tamron 17-50mm, but the performance of the Tammy is better.
The reason is that it is cheaper to produce a cropped sensor lenses.
Why buy a FF zoom lens when you are only using the 50% area of the lens and waste the rest. Unless you are talking about pro FF 2.8 zoom lens like your 80-200f2.8 which can last, or you are switch to FF in the near future.