Quantity Discounts and Price Factor

Here is the problem...

We have many products that all rely on quantity-based pricing. Most of the attributes simply affect price by a flat fee or per unit. However, we have many items whose unit price needs to be affected by percentage increase based on the quantity pricing.

I understand how to use the factor and offset and it works exactly as expected on the first column of quantity pricing. Unfortunately, regardless of quantity, the percentage increase is always calculated on the base price.

How (we think) price factor should work:
100 units @ 2.50 ea + 20% = 3.00 ea
1000 units @ 0.50 ea + 20% = 0.60 ea

How ZC calculates the price factor:
100 units @ 2.50 ea + 20% = 3.00 ea
1000 units @ 0.50 ea + 20% = 1.00 ea

ZC calculates the price factor and offset on the base price but seems to ignore quantity based pricing in this calculation. :yuck:

Am I just misunderstanding how this is supposed to work, or is this possibly an oversight in the price factor calculation when quantity discounts are in effect?

Items are still being added to the store, so if you need an example to play with the "add to cart" feature to see it happening, just let me know.

FYI: When the price factor is displayed next to an attribute, it will look like a flat per-unit upcharge, even though it is a percentage increase.

An URL to a Product and the settings on your Attributes would help to see what you might be doing wrong ...

http://zencart.ebspromo.com/index.php?main_page=product_info&products_id=6

The "Rush Production" attribute has a price factor of 0.2 (20%). The calculation is only figured for the first column's price as opposed to the price of the quantity added to the cart.

You will need to add a few different variations to the cart so you can see my point.

Are the Products marked Price by Attribute YES or NO?

I need more details on the way the attributes are setup on the pricing for this product and what you think should happen at different quanties and what I can see happen when I use those same quantities to see what might be working for you or not working for you ...

Assume I know nothing about your products and that I am very very slow ... :cool:

Price by Attribute: No
Discount Qty Applies to Mixed Attributes: Yes
Discount Type: Actual Price

1st Column: Regular Product Price (1.55) w/ 250 min qty
2nd Column: qty: 500; value: 1.45
3rd Column: qty: 1000; value: 1.40

Rush Production: Factor: 0.2 (all other values are 0, flags set to defaults)

So we would expect the rush attribute to be calculated as follows:
250 - 499: 1.55 + 20% = 1.86 ea
500 - 999: 1.45 + 20% = 1.74 ea
1000 or more: 1.40 + 20% = 1.68 ea

But instead, we get the following:
250 - 499: 1.55 + rush = 1.86 ea
500 - 999: 1.45 + rush = 1.76 ea (0.02 over)
1000 or more: 1.40 + rush = 1.71 ea (0.03 over)

I know it does not seem like a big deal, but we have items that have wide range of qty breaks (example: http://zencart.ebspromo.com/index.php?main_page=product_free_shipping_info&products_id=1) which make cause factor calculations to bee much further off (eg: +0.50 regardless of quantity in cart). That is just an wide qty range example (item 1's rush attribute is just a flat fee) but I think it helps make the point.

When you play around with adding the product (item 6) with "Rush Production" the charge should (i think) be 20% (as set in price factor) of the quantity price. Not just the base price alone.

I can understand why this would work for a general store (1 item at a time) but the various capabilities which allow a wholesale store would lead me to believe this should work as (we) expected.

ZC is a great product and this is the only thing we think may not be quite right. Otherwise, it does everything else just fine... a lot of steps, but far better than everything else we have attempted to use from other vendors. :D

Not to mention, it kept us from writing a new in-house solution. :thumbsup:

Price factor is based on 20% x products_price

It is not setup at this time to base this on a combo of the products_price + all other attributes ...

You might look at the:
Attributes Qty Price Discount:

And at the:
Onetime Attributes Qty Price Discount:

And see if this can get you closer to the Rush charge that you are looking to establish ...

We are not looking for it to do a combo. Percentage price increases are calculated before the options in our case. The problem is that it does not calculate the factor on the right price. The factor should apply to the quantity being ordered, not just the base price of the product. I would think anything that is based on a percentage should work that way if quantity pricing is in effect.

I personally don't want to make any more changes to the price display/calculations than we already have. ZC does a few things that did not make sense in terms of selling products, but we "fixed" those issues. This one is more of a problem because we suspect modding the code to look at the "zen_get_products_discount_price_qty" instead of "zen_get_products_display_price" in shopping cart calculations will be much more cumbersome.

That said, we are trying to avoid what may become a major edit that will ultimately be rendered useless on future upgrades. :down:

Think of this in terms of a product that has quantity pricing and only the 0.2 price factor attribute. The other options do not matter in regards to the issue at hand.

Doing so may simplify things a bit. Either that or I can add a dummy product with only the one attribute and quantity pricing.

Here is a better example of the problem.

http://zencart.ebspromo.com/index.php?main_page=product_info&cPath=4&products_id=7

If you add 500 to your cart w/o rush and 500 with it, you will see why this is a problem. Since there is a significant difference in price from one qty to the next, price factor cannot be utilized because it uses the wrong price in these calculations.

When quantity discounts are in effect, "zen_get_products_discount_price_qty" should be used in place of "zen_get_products_display_price" IMO