I trade options in both Fidelity (IRA) and IBKR (taxable). I recently place a trade for a diagonal call on DPZ. Fidelity showed an average price for the call at $68.65. I placed the order and it almost immediately executed. At the very same time IBKR showed the average price at $71.57. Why can Fidelity get a price of $68.65 at the same time IBKR shows a price of $71.57 (I tried to execute the IBKR at $68.65 and it won't execute)