Not sure what Stackry is... looks like it's limited to buying from certain retailers and then dealing with the Stackry logistics? idk...
Stackry is a US-based parcel forwarding company. I live in the UK and some US companies don't ship internationally, so when I buy stuff from those companies I get it sent to a postbox at Stackry, who then either forward the parcel to me directly, or they can repackage multiple smaller parcels into a larger one, to save on total shipping costs.
I mentioned them because it was through Stackry that I got a very good price on DHL's "Global Mail Direct" service. Having just looked up some direct quotes from US shipping companies, I'm guessing that Stackry get special rates due to the volume they ship.
Even still, it might be worth looking into sending your international parcels via Stackry, you can find their shipping prices on this page
Shipping calculator | Stackry
Admittedly, Stackry's own "reliability rating" is pretty unflattering to the Global Mail services, but my items were fully tracked and insured, and I didn't have any issues. They also offer "Connect by FedEx" option for a bit more money (although still significantly cheaper than the other shipping options), if you're really concerned about using the Global Mail service.
Attached is a screenshot of the quotes I just got for shipping a 5lb parcel from the US to the UK, Stackry add some fees on for relabelling or repackaging (if necessary), but you're looking at $10 tops.