Honestly, the cost varies because the quality of the accountant varies. Also, when you hire a "CPA" most of the time people dont think to ask the CPA what their background is. CPAs are broken into three types of people. There are tax guys, auditors, and advisory guys. If you're dealing with a guy that was an auditor or in advisory, then you're hiring the wrong guy because he doesnt know his ass from his nose.
This is BY FAR the most common mistake when people hire accountants because they dont understand the industry.
If you're hiring a "big 4" firm like pwc, kpmg, deloitte or e&y then their standard hourly rate is 375 per hour for a 1st year associate (fresh college grad). But, they never get to charge the full standard rate, so the real rate is probably closer to $250 per hour or (70% to 50% of the standard rate.) Senior Associates have two years experience cost $450, Mgrs and Sr. Mgrs cost about 600 and Partners cost about 800 to 900 per hour. All amounts are standard rates multiply the rate by 50% or 70% to know the effective rates.
For smaller size accounting firms, the price also varies because the accountant is going to charge based upon their experience and how they perceive their value.
I won't lie, I charge high rates because I think that I provide more value than your average tax accountant. A quick story on how I started my firm:
I charged 20 bucks per return during the first month I opened my firm because I was TERRIFIED and DESPERATE for clients. I got a few because I was so god damn cheap, but I was killing myself for literally NO MONEY. Obviously, this wasn't the way to do things. I very quickly learned a few things.
(1) Don't cheat yourself and charge ridiculously low prices because you dont get more clients. People question your skill and lack respect for you because you're so cheap. Charging will definitely lend credibility.
(2) You need to take a lot of time to ascertain how much the market is willing to pay for your services. In my case, I really didnt know how to quantify this so I just started raising my rates.
The second month I opened my firm, I raised my rates to 150-200 dollars per return. This was better but still not worth the time. This price point actually led to MORE clients and MORE sales.
Lastly, the 3rd month I basically started to just play games and REALLY push the envelope. I wanted to know what the market would accept for my services so i began to quote $3000 starting price for my services to test the waters. LOL. Again, my business didn't slow down at all. By now referrals were coming in left and right to the point where I actually had to SHUT DOWN my website so that I would stop getting calls.
Recap: $20 to $150 to $3,000 haha.
I generally dont charge hourly because people like certainty, I won't rehash this discussion because this point has been beaten to death by coders discussing how they handle consulting jobs. But, I'd say my hourly rate varies depending on the project. The lowest I'd accept generally would probably be around $75 dollars an hour? If it was for someone I liked or for a good cause I've been known to drop the price significantly.