2 x type1      (100+100) -> 1 x type2
type1 + type3  (100+300) -> 1 x type4
type3 + type4  (300+400) -> 1 x type6 + 1 x type2

1 type6 + 1 type2 + 1 type1 -> 1 x type6 + 1 x type3

var types= {
    b1: {price:100,quantity:0},
    b2: {price:200,quantity:0},
    b3: {price:300,quantity:0},
    b4: {price:400,quantity:0},
    b5: {price:500,quantity:0},
    b6: {price:500,quantity:0}
}
function getTotal() {
    var total = 0;
    $.each(types,function(typeId,type) {
        total+=type.quantity*type.price;
    });
    return total
}
$(function() {
    var cont = $("#container");
    $.each(types,function(typeId,type) {
        $('<button class="add" id="'+typeId+'add">Add to '+typeId+'<button><span id="'+typeId+'val">0</button><button class="remove" id="'+typeId+'remove">Remove from '+typeId+'</button><span id="'+typeId+'total">0</span><br/>').appendTo(cont);
    });
    $(".add").on("click",function() {
        var id = this.id.replace("add",""),type=types[id];
        type.quantity++;
        var subTotal = type.quantity*type.price;
        $("#"+id+"val").text(type.quantity);
        $("#"+id+"total").text(subTotal);
        $("#total").text(getTotal());
    });
    $(".remove").on("click",function() {
        var id = this.id.replace("remove",""),type=types[id];
        if (type.quantity>0) type.quantity--;
        var subTotal = type.quantity*type.price;
        $("#"+id+"val").text(type.quantity);
        $("#"+id+"total").text(subTotal);
        $("#total").text(getTotal());
    });
});