well in my experience the top
SEO guys Earn a great deal of money,in fact I would say one of the highest paying jobs in the computer industry.
But to earn top money you have to be pretty sure of your abilities.
If you can get people onto page 1 of google for competative keywords ,the sky is the limit,as for an online shop or many other industries that use the search engines to obtain work or sales being on page one is what it's all about.
Most
SEO consultants I know charge about £650 a day.
Hope that helps.