What is hosting?
Hosting is paying for a computer somewhere else to keep your site or app switched on and reachable, day and night, without your own computer being involved. It is the one part of building software that genuinely has an ongoing cost, because somebody is running a machine for you continuously.
This is why "build an app for free" is usually only half true. Building can genuinely cost nothing. Keeping the result online for other people cannot, because electricity, machines and bandwidth are real. Anybody promising both for nothing is either subsidising you for now or counting something you have not noticed yet.
Ura is deliberate about which half is which: building is free and unmetered, and hosting is the bill, starting at £10 a month. That way the price only appears when something real is running.
How much should hosting cost for a small site?
A small site with modest traffic costs very little to run, and many providers give a free tier that covers it. What pushes the number up is a database that never sleeps, heavy traffic, or large files being served. Watch those three rather than the headline price.