I do this for a living so I can give you an honest answer. Most will charge depending on 1) where they live and 2) how badly they need the business.
For example, when I lived in Los Angeles, I would charge more because it costs more to live there. I live in PA now so I dont have as many expenses (office, parking, etc). At the same rate, someone over seas may not charge nearly the same as someone here in the US.
One thing to note, ANYONE can become a Google AdWords Certified Professional now. They took a lot of the mandatory guidelines away, I think you only have to manage $1,000 over 90 days which is nothing. I do about $500k/mo through my MCC.
Honestly too, it depends on the work. I know it sounds silly, but if you were to ask me to manage 100 accounts spending $1,000 a month, I would charge you probably 2x or more than managing 2 accounts spending $50k a month.
If you have questions, hit me up. I've been in this field for 7 years and know WAY to much about paid search
