What you are talking about is called Table Rate Shipping which will give you better control for e-commerce.
There are some very good ecommerce solutions for WordPress including
- WooCommerce – free and has premium extentions like table rate
shipping and themes – Sth African parent company with 30++
ecommerce extensions and 90+ WP themes - Jigoshop – free and WooCommerce was forked
from this – UK based company - WordPress ecommerce by Get Shopped
is one of the best known and oldest options around. It has a free and premium
versions – NZ based company - WPMU – Aus based company has an annual premium membership fee which meets most of your needs
Personally I think choice comes down to other factors
- Payment gateways (who they want to use for payment and is there an extension for them.
- Payment options & subscriptions (one off, monthly recurring)
- How technical / skilled is your customer for setting up and managing an e-commerce shop.
- What other marketing / sales promotions will they want (like cross linking / upselling content)
- Do you need to manage variations of the same product (by colour or size / weight / length)
- Delivery options / couriers – eg Royal Mail here in the UK, has a plugin for WooCommerce
to be honest … I can say it is likely that GetShopped or WooCommerce can do all of these so it will be a matter of adding up the premium / plugins costs.
There are plenty of other WordPress ecommerce solutions, but many of them will not meet all 5 of these requirements
…
and dare I say it … you should always compare this to Magento which is also a LAMP stack / PHP / Apache / SQL based ecommerce solution.