Help! Extensions!

I'll be needing extensions for the day of the wedding but my hair lady is charging alot for them ($200 just for the extensions, doesn't include her fee for doing my hair)... I don't know what the going rate for extensions are so I don't know if that's a normal price but it's not within my budget

SOOOO, Is it ok to buy them myself at a place like sally beauty for cheaper and ask her to use those?? Or is that considered rude?

And if it is ok, what should I look for, I want very natural looking ones made of human hair...

Yes I'm an extension virgin lol so ladies please help pop my cherry!

Thanks!!