Thanks!
The smart pricing is not on though.
The following was the answer I got from an AirBnB Expert:
======
Please be advised that search result page pricing now includes any additional fees you have set on your listing, pro-rated across the term of the proposed booking. This includes a cleaning fee and any additional guest fees.
For example, a base price of $100 per night with a $50 cleaning fee will display as $125 a night for a 2 night booking.
======
This explains why people might see price differently. It doesn't really explain why the guest saw $67/night (my price is $50/night, $10 cleaning fee, and $10 for second guest/night). But I understand better now.
Huei