the two lens by Sigma, I think are not made by them anymore. I could not find them on their web sight. But from what I could gather, the Sigma 70-300, people were/are buying them for under $200. Now it does have a rating of 4 0f 5 on this site. But that, I feel is not a good rating.
The Sigma 28-80 I found on Sigma for Less at $54.xx.
I really know what you are going through.


rovowen