Are you implying than developers working on site are never late? This is far from true.
Edit: To the downvoters, please explain, I may be misguided.
I'm implying that when you factor in the lack of time zone differences, communications issues, and the increased efficiency of having your employee in the same office as you, then you'll probably get the work done in half the time.
I didn't even touch the fact that your options domestically are far more expansive if you want to hire a high quality developer who will get the job done in a fraction of the time, producing maintainable, high quality code.
Even that's only the case if your office is designed for software/creative work. If it's a noisy, open-office plan full of interruptions and distractions, it's no guarantee that on-site software developers will be more productive than someone working remotely from a library or home office or the like.