The question which is posed in the headline of this post is quite difficult to answer. In fact, the answer will depend on what exactly you will need the speakers to do. Therefore, it is essential to do some research on suitable models before you can start hunting for the best performance. I will cover few applications and recommend some speakers which are typically used within these applications.
Let’s start by looking at some outdoor models. They are quite a few wireless models for this type of application which you can find. When searching for outdoor speaker types, you will obviously have to keep in mind that the speaker has to be rugged enough to be able to withstand weather. That means that the enclosure of the speaker should be sealed in order to prevent water from creeping inside the speaker.
Next you will have to keep in mind that depending on the location of the transmitter base and the speaker, the wireless range must match the distance and ideally be at least twice that. Therefore when doing research pay close attention to the wireless performance specs. However, keep in mind that the actual range may differ depending on your environment. In particular, people walking in between the transmitter and the speaker will tend to reduce the effective range. Also, wireless interference which can occur if there are other wireless devices nearby can degrade wireless performance.
I would stay away from very inexpensive speakers if you are looking at an outdoor application. That is because chances are that such speakers are made from sheep materials which are not able to last over time. In addition to the speakers being rugged, you also have to make sure that the mounting hardware is made from non-rusting material. Also, the speaker has to be mounted so that it will not fall from its location during times of strong winds.
I would say that you should budget at least $100-$200 per speaker if you are looking at an outdoor set up. If you want to you speakers indoors then you can easily get by speakers costing less than $100. In fact, nowadays there are Bluetooth speakers available which cost less than $10. But going back to the price-performance question, do these inexpensive speakers really live up to your expectations? Most likely you will not be satisfied performance of the speakers. Therefore I would recommend testing the speaker before you purchase them.