Pricing by cumulative hours in cart

I'm setting up a store for a school. Pricing is done by the hour, but it is:

1. Nonlinear - no formula; must be done via lookup table
2. Cumulative - so the third 1.5 hour product has a different price than first or second

For example:
1.0 hour of classes = $100
2.0 hrs of classes = $186
3.0 hrs of classes = $263

So if I set three 1 hour classes with price = $100, that's only correct if it's the only class in the cart. When adding the second one hour class, the price should be $86.

Furthermore, if the first class is removed, the price of the second item needs to revert from $86 to $100.

I'm assuming this can't be done without writing some custom code, which I'm fine to do -- but I'd like pointers on how to proceed, if anyone has any tips :-)

Should I

1. use the Notify/Observer framework to adjust prices as items are moved in/out of the cart... or
2. modify whatever code does the cart totallling, or
3. use a custom Payment or Order Total module?
   Thanks in advance,

Mike

Are these additional hours for the same class(product) or for separate classes(products) added to the cart?

These are for different classes/products, which need to remain distinct in the cart.

I actually did a horrible hack in OSCommerce a while back, which was:

• Each class priced @ $0
• When a class item was added, another item called "Classes Total Rate" (or some such) was added automatically; that item was used to carry the price.
• So in my earlier example, with 3 one hour classes, each would be priced @ zero, and a fourth item, "Classes Total Rate", uneditable by user, would be priced @ $263, the sum of (discounted) hourly rates.

I'm hoping to have a cleaner solution w/ ZC. Partly because ZC itself looks much, much cleaner; also because I don't remember how I did it, what files I modified, etc. in OSC way back when... my docs & such were lost in the interim.

Ideally:

• In the product listing, class prices would show the next incremental cost, as a function of what's already in the cart.
• Once in the cart, each item would show that cost too, so the customer sees the discounted price on the second item, rather than just a stark total, as in my earlier solution

Are "Product Types" a way to do this??? Does a new ProdType allow associated pricing code to override the standard pricing?

The classes must co-exist with conventional, fixed price items, btw....

Thanks for the followup!

In the product listing, class prices would show the next incremental cost, as a function of what's already in the cart.
This one is gonna require too much coding to track and dynamically alter prices between products - Would have to be an item that one can just not live without to spend the time/money to create this
Once in the cart, each item would show that cost too, so the customer sees the discounted price on the second item, rather than just a stark total, as in my earlier solution
This also is a stretch as just as with OSC(which Zen Cart is based upon), each product is unique in of itself and doing discounts across products will require custom coding....

shopping_cart.php is the most probable file to begin looking at how the products and resulting prices are summed up

Not impossible but then again not easy nor a subject that can be covered in a couple of posts on a forum

Well, thanks for the input. Although it was even less encouraging than I had anticipated :cry:

Actually, I had really been hoping for some sample code :smartalec: <jk>

Most of what I do remember about my OSC endeavor is hacking away at it every free moment for a solid week to make something bare bones work, so I certainly wasn't expecting it to be easy.

I'm mildly surprised that I haven't seen anyone else that seems to be selling services (vs products) using ZC. Is there another product out there that I should know about, more tailored to the service industry???

Thanks again,

xenophile

kobra:

This one is gonna require too much coding to track and dynamically alter prices between products - Would have to be an item that one can just not live without to spend the time/money to create this

This also is a stretch as just as with OSC(which Zen Cart is based upon), each product is unique in of itself and doing discounts across products will require custom coding....

shopping_cart.php is the most probable file to begin looking at how the products and resulting prices are summed up

Not impossible but then again not easy nor a subject that can be covered in a couple of posts on a forum