<select id="chto" onchange="chtom.value=this.value;">
<option value="">выберите</option>
<option id="bag" value="10">bag</option>
<option id="t-shirt" value="20">t-shirt</option>
<option id="shose" value="30">shose</option>
<option id="shirt" value="40">shirt</option>
<option id="pen" value="50">pen</option>
</select>
<input type="text" id="chtom">