The performance of your website is directly tied to the revenue you get from it. It’s a multiplication of all the work you’ve put into it. The faster your site, the more money you earn from it.
The good thing is, you have a direct influence over the performance of your WordPress website. You can make it faster by yourself, but it’s a relatively specialist task. So it could make sense to hire someone like me, who specializes in making things fast.
How many resources should you invest? It depends on the type of site. If you are running an e-commerce store, you will naturally invest more than into a one-pager about your local freelance business.