I am a pro web designer, so I'll hire myself.
Literally that is what it is. If I can earn more money designing my website myself than I could doing other things, then I'm making the website. If my business is about Something Totally Different than designing a forum or a blog and I could earn more money doing the Something Totally Different than in web design, time to outsource.
But I think that I will be making my own websites for the foreseeable future. Unless I don't know the particular tech, then I'll get pro help for the first rodeo so I can learn to properly do it myself. I both esteem and pity anyone who ends up with me as web design client, because I know what I'm doing. That makes communication easier, but if you don't do it right and try to take shortcuts, punishment will be swift indeed. *grins savagely*
If you are here to stay for long, i.e. run a website for many years, you need to learn website designing, this not reduces your cost of website management
It should be noted that website designing, whether you hire an outside organization to do it or pursue an internal hire, is likely a long-term relationship if you don't want to learn to web design yourself.
If you are trying to launch a simple blog, I think you can do this yourself even if you do not have skills and knowledge (learn from youtube), but for ecommerce you need to hire a designer.
Eh, you can probably use Shopify without much trouble, or the Woo Commerce Wordpress plugin can connect to a lot of payment processors. For a small ecommerce store, learn Wordpress, self-host it, use Woo Commerce and your processor of choice to set up your store, and then use the blogging half of Wordpress to write articles to attract users via SEO.