It’s not easy to shop for hosting because the quality is not always evident upfront. It’s not as obvious as the below scenario.
Beyond quality, it’s also unclear how much power and scope a site will require in memory, storage capacity, CPU, and bandwidth. Of course, it’s possible – and particularly speedy in scalability-friendly cloud server hosting situations – to change parameters after the fact, but it’s easier to set up your infrastructure with enough room to serve visitors sufficiently and grow.
When looking at bandwidth specifically, web hosts sometimes have packages that offer a terabyte of bandwidth. A terabyte sure sounds like a lot, but calculating how closely a terabyte comes to meeting your needs will give you a sense whether to initially select that option.