Sell products with different prices for different quantity

Need a form for a site that sells firewood and the price changes depending on quantity, the larger quantity you purchase, the lower the price. Here is an example.

Oak Firewood
1/4 cord $50
1/2 cord $90
1 full cord or more $150

Juniper Firewood
1/4 cord $70
1/2 cord $125
1 full cord $200 per

So we will have like 8 different types of wood and each have different pricing.

This is easy to setup by setting the prices for each quantity and they choose a quantity from a drop down. But the problem I have is what if they order 1/2 cord of 2 different types of wood? Since they would have a total of 1 cord in the cart, it should change the pricing of each to the 1 cord price and NOT the 1/2 cord price.

So the total quantity ordered determines the final price.

I wrote a simple php form that did this form me many years ago but doesn’t allow for different prices if multiple types of wood in different quanties are ordered. If they just order 1 type of wood then its no problem.
https://paulbunyansfirewood.com/order-online/

Any tips on what I could use to build an order form in wordpress?

An ecommerce plugin or gravity forms with conditional logic?
Or maybe I need to find a freelancer to create something custom or maybe update my current order form which is here: https://paulbunyansfirewood.com/order-online/
?

I guess it would be easier if they just offered a flat percentage discount based on quantity ordered but the client sometimes has random pricing for different types of wood based on supply & demand.

Thanks!!!