That's great but a PC can't run OS X...
Well you see you didn't give us much information about your setup / workflow / situation. Our video guys can't lug a Mac Pro tower around to locations. Just not feasible. Carrying an external GPU does work. That works for them. Hackintoshing is not something that is viable in an office setting.
Your tone is going in the wrong direction. It's not "wtf. Why can't Macs to this? A PC can do it and for $****". This is a place to ask, "I want a MacBook Pro, how can I get it with pro graphics?"
We can't help that Apple doesn't supply you with what you want but we can do our best to provide a solution (No consultation charge too!)
Also not all businesses need workstation / pro graphics cards.
Link Thus the term "business graphics card" doesn't make sense.
Laptops also have more uses than just run applications that benefit from specialized hardware accelerated graphics. For example I primarily use my laptop for PHP and web development type work. I get plenty of use out of it. No where close to useless.
There is no cheaper alternative than buying a Mac. No other manufacturer sells computers that runs OS X.