I had this lens, checked, cleaned and tested by Canon UK last August.
Whilst I agree that this lens is now discontinued, or replaced by the later model, there are still a limited amount of spares available.
So provided it is looked after (as I have done) it should produce top quality images for many years to come.
However, given it’s age, no USM etc and the lack of any repair possibilities for significant parts (per Canon) I wouldn’t take the chance at that price.
I have a few contacts in Camera Club circles that have offered more than that.
Also, I would also not be really happy to post this as sometimes things go missing,……. mysteriously !
If something is worth while getting, I have no problem driving across the country to view and try out first.