First, it delays the host generating the ARP to wait on a response before it can forward a frame. (Hence why there's an ARP cache.)
Second, it's a broadcast, so all hosts within the broadcast domain will receive it and need to examine it. This consumes both bandwidth and the host receiving it, its resources. (Hence another reason why there's an ARP cache.)
Lastly, switches need to replicate a received broadcast to all other ports within the same broadcast domain. Which, depending on the switch architecture's hardware, might impact its resources. NB: This is usually not a problem. More so, if the switch has an IP as within the broadcast domain, it too needs to process the received broadcast, like other hosts. This would probably be done on the "control plane" and such's supporting resources are often much more limited than the "date plane" resources.
