How to get an added value from multiple checkboxes in javascript/jquery?

I have multiple checkboxes added with a button. I want to assign a value of 150 for each checkbox that is checked. Maybe my logic is wrong, but i cant get it working. Ideas?

function getValues() {

    var cost = 0;
    var isChecked = $('.isLab').prop('checked');

    $('.isLab').each(function () {
        if (isChecked == true) {
            cost = 150
        }
    });
    alert(cost);
}