Why this function is called multiple times in Jetpack Compose?

I'm currently trying out Android Compose. I have a Text that shows price of a crypto coin. If a price goes up the color of a text should be green, but if a price goes down it should be red. The function is called when a user clicks a button. The problem is that the function showPrice() is called multiple times (sometimes just once, sometimes 2-4 times). And because of that the user can see the wrong color. What can I do to ensure that it's only called once?

MainActivity:

@Composable
fun MainScreen() {
    val priceLiveData by viewModel.trackLiveData.observeAsState()
    val price = priceLiveData ?: return

    when (price) {
                is ViewState.Response -> showPrice(price = price.data)
                is ViewState.Error -> showError(price.text)
            }

    Button(onClick = {viewModel.post()} )
}

@Composable
private fun showPrice(price: Double) {
    lastPrice = sharedPref.getFloat("eth", 0f).toDouble()
    val color by animateColorAsState(if (price >= (lastPrice)) Color.Green else 
Color.Red)
    Log.v("TAG", "last=$lastPrice new = $price")
    editor.putFloat("eth", price.toFloat()).apply()
    Text(
          text = price.toString(),
          color = color,
          fontSize = 28.sp,
          fontFamily = fontFamily,
          fontWeight = FontWeight.Bold
      )
 }

ViewModel:

  @HiltViewModel
  class MyViewModel @Inject constructor(
    private val repository: Repository
): ViewModel() {

   private val _trackLiveData: MutableLiveData<ViewState<Double>> = MutableLiveData()
   val trackLiveData: LiveData<ViewState<Double>>
       get() = _trackLiveData

   fun post(
   ) = viewModelScope.launch(Dispatchers.Default) {
       try {
           val response = repository.post()
           _trackLiveData.postValue(ViewState.Response(response.rate.round(7)))
       } catch (e: Exception) {
           _trackLiveData.postValue(ViewState.Error())
           Log.v("TAG: viewmodelPost", e.message.toString())
    }
  }
}

ViewState:

sealed class ViewState<out T : Any> {
    class Response<out T : Any>(val data: T): ViewState<T>()
    class Error(val text:String = "Unknown error"): ViewState<Nothing>()
}

So when I press Button to call showPrice(). I can see these lines on Log:

2021-06-10 16:39:18.407 16781-16781/com.myapp.myapp V/TAG: last=2532.375732421875 new = 2532.7403716
2021-06-10 16:39:18.438 16781-16781/com.myapp.myapp V/TAG: last=2532.740478515625 new = 2532.7403716
2021-06-10 16:39:18.520 16781-16781/com.myapp.myapp V/TAG: last=2532.740478515625 new = 2532.7403716