I'm not sure about VueJS specifically, but I run everything I can off a $6/m digital ocean droplet (static sites, web apps, git repos, RDBMS, some other custom apps I've written) and it hasn't broken a sweat yet[1].
My understanding used to be that requests will be dropped if my virtual server can't handle it, and I'll have to transfer 10,000TB to get to a $100,000 bill.
In practice, my server will not physically handle the load to serve more than maybe $1000 of data a month; it will fall over before that.
In summary, using a VPS is sorta like an instant hard cap.
[1] Until I tried using Jenkins. Which crashed constantly because apparently 512GB of RAM is too little for what it does. I'm now in the process of writing my own little CD tool that isn't going to go over 30MB of RAM just to run my deployment scripts.
This is the big thing, but I also think that modern out-the-box OSes are pretty damn secure these days.
IOW, the amount of knowledge and time needed to maintain my single VPS is a lot less than the knowledge and time you will need to manage your costs using multiple hosted SaaS suppliers for static hosting, web-app hosting, database hosting, repo hosting, etc.