It is a constant with many purchases I make. How far or how deep do we dig to answer the question is the question. I collect NHRA Drag Racing 1/24 Scale Die cast Cars. I niche marketed them for years by gettnig the driver signatures on them. Any hoot. The cars were purchased from suppliers or vendors on Ebay here in States, usually. Yet, the cars are made in China. I know not what you asked?
I have two fountains in the back garden and the pumps / solar power cell kit is from a vendor in China I use annually on Ebay. I purchase three pump kits annually - I change them out annually. The pumps work fine and the workmanship and quality is there, I do it as maintenace because of the grime that occurs with birds bathing in the water and such.
I puchased collectibles from the UK and Austrailia too. Again, it is usually drag racing memorbillia. Drag racing is an international sport with fans world wide. I have purchased aqarium components from both Japan and New Zeland. One thing to remember is they offer different shipping alternatives just like US vendors. A common occurance is when a purchase price exceeds a set dollar amount they at times offer a quicker shipping experience at the original shipping cost. It varies.
Also, I would venture a guess that my international business ranged from 12 - 15% when I operated the store on Ebay. This question has prompted me to look into when time allows the amount spent overseas and the amount earned from overseas sales. I wonder.
Regarding Transactions with Ebay I have only had one negative experience since 2005 and it was with a US vendor. Long story.