I shipped to UK, Ireland and Australia regularly, and USPS was in fact the cheapest. Depending on how heavy your shipment is, 8 OZ is $7.20. How many shirts are you shipping? I don't understand what you mean about you don't think the USPS will "ship out there", but there wasn't anywhere in the UK that the USPS wouldn't ship.
I don't think Fed Ex or UPS gives discounts for having an EIN number, I could be wrong, but I would think any discount would go to contract customers with heavy volume.
If you need any more help with USPS shipping to UK, just write. I've done alot of shipments there. I wouldn't mind helping you out. Best regards.
I just don't have much shipping experience, especially outside of the US. I thougth United States Parcel Service would just do shipping inside the US, my mistake im worn out from lack of sleep and did't think that out very much.
I found USPS to be cheaper for me in general and will go with them.
Do they provide bags or boxes for me to ship in? I haven't purchased any supplies for shipping yet. Shirts weight 6 oz or less. Only shipping one shirt this time around.
I just don't have much shipping experience, especially outside of the US. I thougth United States Parcel Service would just do shipping inside the US, my mistake im worn out from lack of sleep and did't think that out very much.
I found USPS to be cheaper for me in general and will go with them.
Do they provide bags or boxes for me to ship in? I haven't purchased any supplies for shipping yet. Shirts weight 6 oz or less. Only shipping one shirt this time around.
USPS supplies boxes and tyvek bags for free if you are shipping Priority Mail, otherwise they have some supplies for sale. My favorite packing is poly bags. They are strong and lightweight. If you can't find anything local, you can get something at an office supply store or even Walmart. Mostly likely you'll find a bubble type envelope available.
A while back I wrote a post regarding shipping, International shipping, USPS, digital scales, custom forms and where I buy poly bags on Ebay for shipping in, along with pricing, I believe. It includes information on setting up an account with USPS for shipping. I'm giving you the link. It's pretty much a run down of how I did my shipping. If you have and Q's after reading it, just LMK. Best regards to you.
Just a heads up for future reference. It ended up costing $9.75 total to ship from NJ to UK, that was the cheapest option. I had to buy a cardboard box/bag type of thing from them for $1.
I just shipped a 2 mens tees, small package box, from CA to UK and it cost me $13. 1 tee from CA - UK $9.04. I have my own mailers etc...so take price and material cost in consideration for when you price your shipping. Hope this helps
I've used BigCartel before, I'm using Storenvy now. It really depends on you because there's more to consider like where are you located vs. where your customer is located. For example shipping from CA to Canada is cheaper for me rather than shipping to the UK. If you're not using Goggle Analytics try using that on BigCartel to see where majority of your Int. traffic is coming from and then charge based on that rather than just guessing. Sorry for not being able to give you a flat $dollar amount....but hope that clears some stuff up for you
shipping overseas 
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