Am Leonard offers free shipping a few times a year so sign up for the email notification.
They are a full service gardening/greenhouse supply company but they don't sell seeds. I buy perlite half the price of local stores and I just ordered 3.8cuft bag of organic seed starting mix for $28. That's a deal for my area so I stock up for future planting.
The free shipping applies to only 80 lbs and they list the weight of the product under the price in the description.
This is good till Sep 3rd so take a look soon.
https://www.amleo.com/