$('.price-selector_option:selected').each(function() {
if($('.price-selector_item').attr('data-select') == $('.price-selector_option:selected').val()) {
$('.price-selector_item').addClass('price-selector_item--selected');
}
});
<div class="price-selector">
<select class="select-input">
<option class="price-selector_option" value="1">
iPhone 4
</option>
<option class="price-selector_option" value="2">
iPhone 4s
</option>
<option class="price-selector_option" value="3">
iPhone 5
</option>
</select>
<section class="select-result">
<table class="price-selector_item" data-select="1">
тут прайс
</table>
<table class="price-selector_item" data-select="2">
тут прайс
</table>
<table class="price-selector_item" data-select="3">
тут прайс
</table>
</section>
</div>
$('.price-selector_item').addClass('price-selector_item--selected');
В переводе на русский:$('select').on('change', function(){
var val = $(this).val()
$('.price-selector_item[data-select='+val+']').show()
.siblings().hide()
})
Вместо show и hide можете использовать addClass() / removeClass()