I see what you're saying, but it might still be useful for them to know what trade-offs are being made.
Like, "for this site and audience, we recommend supporting IE6. But FYI, that does eat this much of our costs, which can't be spent on shiny new features for modern browsers. So maybe for other projects, if you do something that targets a different audience, we'll want to make a different trade-off."
If I were the client, I think I'd appreciate that info. It might affect what types of sites I want to launch, for example.
If big companies are part of your core audience, they are part of your core audience. At that point IE 6 support is not optional, nor is pushing back on it going to make a difference. All you'll do is cause annoyance.
Like, "for this site and audience, we recommend supporting IE6. But FYI, that does eat this much of our costs, which can't be spent on shiny new features for modern browsers. So maybe for other projects, if you do something that targets a different audience, we'll want to make a different trade-off."
If I were the client, I think I'd appreciate that info. It might affect what types of sites I want to launch, for example.