ShopAround:

I've also shopped in Italy, and GB commission was around 50%.

They have an online cacluator: http://www.globalblue.com/tax-free-s...nd-calculator/
I've just keyed-in a 200EUR purchase. The VAT rate in Italy is 22%, so the refund should be 44EUR, while the calculator shows a 25EUR refund, or a 12.5%, which is roughly half. The other half is of course GB's fee.

I don't see why a 3rd party must be involved in the process since the VAT is collected and refunded by the government. I understand they charge a premium for a speedy processing that is required, but if one is not in a hurry why pay a commission to a middleman?.