Working demo: http://jsfiddle.net/j051rkkh/1/ new: http://jsfiddle.net/j051rkkh/3/

perks_selection.js

$(function() { // shorthand for $(document).ready()

    // get all checkboxes
    var allCheckboxes = $(".perk:checkbox");

    // group them by name for later
    var groups = {};
    allCheckboxes.each(function() {
        groups[this.name] || (groups[this.name] = []);
        groups[this.name].push(this);
    });

    // hook up event handling
    allCheckboxes.on("change", function(event) {
        // reset all checkboxes (easier than having to reset)
        allCheckboxes.each(function() {
            this.checked = false
        });

        // get the clicked checkbox and its amount
        var selected = $(this).prop("checked", true);
        var amount = selected.data("amount");

        // process each group of checkboxes
        for (var name in groups) {
            if (!groups.hasOwnProperty(name)) {
                continue
            }

            var group = $(groups[name]);

            // get those checkboxes in the group that have an equal or lower amount
            var matching = group.filter(function() {
                return $(this).data("amount") <= amount;
            });

            // get the maximum within that
            var amounts = matching.map(function() {
                return $(this).data("amount");
            }).get();

            var maxAmount = Math.max.apply(null, amounts);

            // now check those that have that amount
            group.filter("[data-amount='" + maxAmount + "']").prop("checked", true);
        }
    });
});