Recommendation: If you're looking for an inexpensive harmonica, go with the Fender Blues Deluxe line (not an affiliate link).
I don't play harmonica often enough or well enough to be willing to fork over for, say, a Hohner Special 20 or Marine Band (not affiliate links). I have a couple of (inherited/gifted) Marine Bands, but you know me -- until this last week, I hadn't paid more than $100 for a guitar in nearly 20 years. Unless I take the time to get a lot better, and start playing the harmonica in public, I'm just not going to pay $40 or so for a harp.
On the other hand, the sub-$10 harmonicas I've bought in the past have uniformly been complete wastes of money. If they're even in tune when they come out of the box, and that's a gamble right there, they require more forceful breathing to get an audible sound out of, aren't very accommodating to "bending" notes, and are likely to blow a reed in the first few minutes of playing.
I'm not just talking about off brands here. Hohner's Piedmont Blues line is just complete crap. A set of seven harps will only set you back $25 (I got mine on sale for $15 on Black Friday a few years ago), but the nice nylon zipper case they come in is the only thing of any real value in the collection. Two of them were unplayable (not in tune) when I pulled them out of the case, I had to huff and puff like the Big Bad Wolf to get them to make noise, and none of them lasted more than a few songs without blowing reeds.
I've purchased two of the Blues Deluxe harps (in G and B-flat). Metal cover plates, not plastic. They feel substantial and seem well built. They're in tune. I can easily bend notes when playing blues cross harp (which is pretty much all I use a harmonica for), and they produce a big sound without me leaving me gasping for air. I haven't blown a reed on one yet.
They'll set you back $12-15 each, or $60 for a set of seven (A, B-Flat, C, D, E, F, G) in a nice case. That's a little bit more than the cheapest harmonicas, but the difference isn't just big enough to matter, it's too big to ignore.