That's really not that much traffic, so I don't think any of them will not be able to serve up so few hits. One of our servers is running on a $40 Linode and served up 186,698 unique visitors, 6,837,460 requests, and 552G of data last week alone and we had no issues with performance (in terms of bandwidth, CPU, memory usage, or disk usage). That Linode is a tad bit beefier than the $5 one, but I doubt you'll run into any issues with 50k visitors on a Ghost blog (which is, from what I saw last year while playing with it, fairly performant and optimized).
If you are going the VPS route, just make sure the provider allows for resizing your instance in case you do end up needing a larger instance.