Wow! So in general he is asking for a $10,000 commission on each transaction no matter what. That is a great business plan but does is work for you the consumer?
If you bought a $100,000 home and the commission was 3% to your buyers agent then his commission would be $3,000. Add the 1/2% he will charge you on the $100,000 which is another $500, totaling $3,500 to your buyer agent. You'd owe him $6,500 or $5,000 since he has your $1,500 refundable retainer fee. (I think I did my math right)
On a $250,000 home you'd have to let him keep the retaianer fee to meet your agreed upon commission structure.
Perhaps what he was subtly telling you was that he is a buyer agent for higher-end homes. That is great for him. Perhaps you will be better matched with a Realtor who sells homes for a more conventional commission.
As a Buyer you really have more important things to worry about than your agent's commission. Our suggestion is to keep your heart and mind focused on what you need to do which is: 1) get qualified to buy, 2) find one agent you like and trust and go shopping for homes, and 3) start packing because it will just be a matter of time before you find a great home !
I love this question because it shows that Realtors and Consumers have choices. God Bless America !