Each item we ship may have different delivery times. This is because some products are packaged and shipped separately. E.g. we send our posters in super-durable tubes. Obviously, a canvas won't fit in there.
Shipping prices are cumulative. When you're calculating shipping prices on your end, make sure to add up the different shipping prices for all of the products you're sending.
For example, you can order a t-shirt with a flat rate shipping price of $5.00. Each additional t-shirt adds $0.75 for shipping. If you add a tote to the order, then it will also cost simply an additional $0.75. However, if you choose another product, like a mug (that requires different packaging), then you'll have to add the full shipping price. In this case, it would be an additional $6.95.