> And if the subcontractor does crappy work, the client will think you did a crappy job.
If you passed through your subcontractors work without reviewing it, you did do a crappy job.
> I would think that if the subcontractor was good enough not to do bad work, he/she would also not want to do IE6 compatibility work.
That's assuming a lot about other peoples priorities. You'll be surprised how many perfectly qualified people who does not place the same premium on creative freedom you do.
If you find yourself with a lot of well-paid IE6 work, spending some time on elance finding someone good to offload it to and putting him on a handsome retainer could turn out to be a very good investment.
If you're jacking up prices in an attempt to drive away business, I think you can afford to buy pretty good work. But if we go by your logic, no good IE6 compatibility work ever gets done, so expectations will be low anyway.
I would think that if the subcontractor was good enough not to do bad work, he/she would also not want to do IE6 compatibility work.