For what it’s worth, I updated a site I’m working on from this:
to this:
Just by installing the Air theme and making minor updates to settings. It’s an improvement, but I expect I’ll be doing a lot of tinkering with it as I develop the site. I’m not happy with the colors and fonts just yet, for example.
When I read “a theme that looks the same as” some other site, all I can think of is scope creep. What elements do you want to copy? Colors and fonts are easy enough. (Though I would say dark gray text on a black background is a violation of my personal code of ethics and I wouldn’t do that. 
) I know how to use the Custom Header Links theme component to add those. Rounded corners isn’t that hard if you know about border-radius. I could see making those changes for $100-150. (Step one could very well be to find a theme that gets close and fork it.)
Trouble is the target theme probably has elements that I’m not seeing right now that might be important to a client. The logo with the gradient (AKA ombré, I think?) looks cool. I can’t help with that. Some users have “PRO” avatar flair. I can help set that up if I’m provided the desired icon, but my graphic design skills are next to non-existent. You get the idea: “looks the same as” isn’t a useful specification (either functional or technical).
From hard experience I can also tell you that there are shortcuts to make a Discourse theme that “looks like” another site. Trouble is, the result is unlikely to be maintainable as Discourse (and the design esthetic of the internet) changes. Creating a theme isn’t something you’d want to pay $100 for. If that’s your budget, you’re better off learning how to do it yourself. As I suggested when you PMed me, you might benefit from just paying for someone to walk you through the process. I strongly suspect it’s the cheapest and fastest way to get what you really want.