Of course a developer isn't a testing environment. Developers don't cost a fixed $300.
If there are differences between IE and (Chrome|Firefox|Opera), then it will require additional developer time. Just testing for those differences will require additional developer time.
I don't want to demonize IE. Supporting any browser requires testing. IE has been especially reluctant to adopt web developer trends and needs to work hard to regain developers' trust. Supporting it isn't just the cost of a testing environment.
If there are differences between IE and (Chrome|Firefox|Opera), then it will require additional developer time. Just testing for those differences will require additional developer time.
I don't want to demonize IE. Supporting any browser requires testing. IE has been especially reluctant to adopt web developer trends and needs to work hard to regain developers' trust. Supporting it isn't just the cost of a testing environment.