It really depends what you want from a host. For example, I have a 1Core/2GB/40GB/2TB plan on Cloudways, based on a VULTR server, and it costs $23/month. If I went directly with VULTR the same plan is $10 a month.
So what does Cloudways provide for that $13 a month? They provide management infrastructure on top of the bare VULTR (or other cloud provider) platform.
If you go with something like VULTR directly you, the user, have to configure and manage everything yourself. Want a database? How about Elasticsearch? Redis? You get to install, configure, and manage those features yourself. Want to host 5 different stores and a development platform on a single server? You get to configure that and set it up. Want a Let's Encrypt SSL certificate, or even better, one for each of your stores which each have several domains/sub domains? You get to set that up and manage it too.
For some people that is fine, for others it is desired or even required. For a lot of people though that's a royal PITA and will lead to a huge mess in short order. Personally I could set that stuff up myself if I had to, and I could learn how to do the parts that I don't already know how to do. Unfortunately I have limited hours in each day and I'm quite busy with other projects. Paying $13/month to have someone else take care of that is a good deal for me at the current time.
Another reason I like Cloudways though is that they do work directly on top of VULTR, and for what I am doing I want to have different servers in different parts of the world. Site focused on Australian customers? Hosted in VULTR's Sydney datacenter. Site focused on UK customers? Set up in London. Likewise for other countries.
So while it is certainly possible to find cheaper hosts than Cloudways they do provide good value to many people.