Digital growth experts are going to cost a pretty penny, simply because they are basically a higher rank of digital marketing experts. Growth experts are all about increasing visibility and gaining followers, so they tend to work mostly on email list building, SEO, PPC advertising, as well as social media following. 

Truth be told, it's hard to nail down what a digital growth expert will charge you, simply because they all have their own price lists and ways that they work. You really need to look at their price list to figure out what you will spend.

With that said, I can ballpark a general idea of what you might be charged at a typical growth agency:

• SEO - $1,000 to $6,000+ per month
• Social Media - $250 to $10,000
• Growth Diagnostic - $250, though some do this for free as a way of marketing their expertise. 
• PPC Advertising -  Between 5 to 20 percent of your ad spend, or a flat rate per month depending on the contract.
• Public Relations - $3,000 to $7,000 per month

While these costs may seem high, there's a lot more to the picture than just the price alone. You have to ask what you're getting, who you're getting it from, and what kind of results you're expecting. You should seriously vet your growth expert, simply because there is no specific qualifier for this title.

If you choose to hire a growth expert, the best thing that I can suggest is that you need to have an airtight contract that outlines precisely what you should expect to see happen. Moreover, you really should avoid any kind of vague promises that they could make. Hard numbers are a true growth expert's best friend.