<div class="block">
    <div class="priceday">10</div>
    <div class="form-text">20</div>
    <input class="summ" type="text" name="summ"  class="form-text">  
</div>

.block {
 background:gray;
}

$('.block').click(function(){
    var price = parseFloat($(this).find('.priceday').html()); 
    var day =  parseFloat($(this).find('.form-text').html()); 
    sum =  day * price
    $(this).find('input.summ').val(sum);
    
 }).trigger("click");



/* С использованием setTimeout - используется |var ids = $(this);|
$(".block").click(function(){
      var ids = $(this);
setTimeout(function() {
    var price = ids.find('.priceday').val();  
    var day = ids.find('.form-text').val(); 
    sum =  day * price
    ids.find('.input.summ').html(sum);
}, 1000);
 }).trigger("click");*/