There's value in having someone else do something for you. Eating at a restaurant is a basic example.
When there's risk involved, you're willing to pay even more. Hiring an electrician or plumber. And the value goes up the more risk there is, just like an insurance premium.
But value can go through the roof when there's a potential for gain on the line. Especially coming from a credible source with a proven track record of success. How much would you pay for a machine that spit out $2 for every $1 you put into it? Even if the total cost of that machine's parts was only $40?
A good consultant can analyze a business, figure out what needs to change, write some decent content, bring it all together in a theme forest template, set up so e traffic sources, and add 5, 6, or 7 figures to a business's bottom line.
Plus, if you're too cheap, they might not even consider you. Would you buy a $20 car? You'd be very skeptical and ask a lot of questions. There's even the weird pricing trough where you just assume it's a scam and move on.
All that to say that charging $500 is more than reasonable. I usually charge 6x-10x more for a superficially similar service (consulting plus template setup and customization). It's all about how you position your service, and what benefit you can guarantee your client.