I do a lot of shopping in Italy and while Global Blue does take a percentage, I've not seen it anywhere near 50%.
I don't see how you could get the VAT back without one of the refund processing companies involved. The retailer generates the form when you make your purchase and they all have specific VAT refund companies they are affiliated with (i.e. Global Blue, Premier). In all my years of shopping in Italy, I can't recall ever seeing a tax refund form that was just from a retailer and not from one of the refund companies.