Don't blame the suppliers for the shipping costs. Ammunition is heavy and delivery is restricted to ground service, not eligible for flat-rate priority mail or other such services.
While bulk mail advertising continues to fill our mailboxes for pennies per pound, and our congress critters retain "franking" privileges allowing them to send propaganda by the ton, the rest of us have to cover the costs when we buy or sell with delivery required.
High volume shippers can negotiate sweet deals with FedEx or UPS, and the US Postal Service offers some nice discounts for big accounts. Those do not apply to smaller businesses, and certainly not to individual sellers.
Several months ago I offered a cartridge case tumbler as a "karma" gift to another forum member. Package was probably 12"X12"X18" and weighed about 12 lbs. Parcel post delivery was $45.50, and USPS busted the package in transit and sent it to a lost mail facility, never delivered to the addressee and no thought of a refund of the postage charges.
Anytime I see "free shipping" I always figure that the cost is being paid another way, and probably by me.