Is CouchSurfing cheaper than staying in a hostel? Actually, this depends somewhat. If you’re going to an area where the hostels are inexpensive, as in around $10 a night or less, it may end up costing you just as much to CouchSurf.
For one thing, you tend to pay more in transportation costs getting to where your hosts live, which is rarely right in the middle of where you want to go. For another, at least if you’re a decent human being, you’ll bring your host some kind of thank-you gift and/or buy the ingredients to make him or her dinner. This could easily be more than $10.
Your host will likely also want to go out at some point, and you should pay at least your own portion of the bill. If you didn’t budget for going out, this could obviously be problematic.
However, your host may end up giving you a ride to some out-of-the-way place you never could have gotten to on your own, or otherwise show you things about the place you’re visiting that you wouldn’t have otherwise seen. It depends a bit how much this and the general CouchSurfing experience is worth to you.
Hostels are typically simpler, much more straightforward, and easier to assess in terms of cleanliness and location with a little online searching. There’s also less of a cultural barrier: it’s known you will pay X amount for X service and that’s that. You can nap in your bunk all day if you’re tired; doing this at a CouchSurf host’s house is a little weird.
Additionally, at a hostel, you can cook in the kitchen (if there is one) without worrying that you’re putting someone out. Pro tip: I sterilize my dishes with hot water from the electric kettle before I use them, because I really don’t trust the bacterial content of the sponges soaking in most hostel kitchens, even the clean hostels. I also remain dubious about the dishwashing skills of most hostel-dwellers. May the spoon you licked clean and then ran under cold water be the one you pick up next time.