US shipping strategy for best price?

I’m looking for hints for how to get the best price for shipping, given I am shipping from the US and my product is inflexible and about 100 x 100 x 30 mm in size? I’ve seen some Tindie products that are apparently [ab]using the USPS media mail service to get cheap rates; is that cool? Is tracking a must have or is it worth the risk to ship using an untracked service? TIA for any suggestions.