Price for a graphic designer will depend on what you need done and what the skill set is, along with the return time.
I've paid between $45 and $1000 for various "quick" jobs that I've needed done. I've paid MUCH higher for full sites (of course) and that was just the TEMPLATE not the actual content!
Turnaround time will affect price. There are three factors - Speed, Quality, Price... pick 2, you can't get all 3!
For low price, and high quality - expect to wait a long time
The important part that you need to discuss with your designer is price and budget range. People often go blind into discussions saying "I want this, and that" - but really the first question should be, how much can you spend - THEN you can adjust accordingly.
If someone came to me with $100, I'll offer then a completely different set of options than someone who comes to be with $1000 in hand. It's not about exploiting the money, that's not what I'm saying. Someone with $100 will get a stock graphic modified to their needs. Someone with $1000 may get either a higher quality graphic or even a CUSTOM graphic all together.
How much do you pay for an oil change? $19 at PepBoys where you wait 3 hours, or $39 at Jiffy Lube where it takes 15 minutes?
They do the same job, just one does it faster!