$("#path_costs").html("Costs:\n<table>\n");
$.each( data.paths, function(key, val){
    $("#path_costs").append("<tr>");
    $.each(val.cost, function(k,v){$("#path_costs").append("<td>"+v+"</td>");});
    $("#path_costs").append("</tr>");
    });
$("#path_costs").append("</table>");


Costs:
<table> </table>
<tr/>
<td>427</td>
<td>1</td>