Excessive Commission on the Sale of Banknotes

The hammer price may be £100. Then add on commission, VAT and postage. The final price can be substantially more. It seems most Auction Houses are charging around 20% – 25% to buyers. Seller premiums are more negotiable. However, at a recent General Auction I bought some banknote Lots and found the commission was 33%, plus VAT and postage. I think this excessive. Buying from me involves no commission whatever…..this cannot be bad. No ‘robbery’ or unseen charges and moreover, free GB postage!