Most cheap solar zappers use weak 500V grids. When a mosquito hits, it only stuns them, meaning they wake up and bite you anyway. On top of that, the fragile plastic casings crack under normal summer heat, letting rainwater seep into the electronics and shorting the battery within a month.
And the listing price is a total trap. Most cheap options ship with sub-par batteries, forcing you into proprietary replacement bulbs and a mandatory starter accessory bundle before you can even hang the unit.
Six months down the road, you run into the replacement battery tax. The built-in cells degrade quickly, and because they are soldered shut, you have to throw the whole machine away. This planned product obsolescence turns a cheap purchase into a recurring annual subscription.