Menu price is not the bill
Many restaurants add a service charge and a tax on top of the menu price. Ask whether the quoted price includes both, and whether the service charge is distributed to staff.
Beverages change the total
Water, soft drinks, coffee and alcohol can add a large share to the bill. Compare the total for the meal you would actually order, not the cheapest main course.
Set menus have rules
A set menu may require a minimum number of guests, a shared table or a specific time. Check what is included and whether substitutions are allowed.
Timing and day of week
Lunch, early dinner and weekday menus can be cheaper than weekend dinner. The same restaurant can have different prices for the same dish at different times.
Keep the local currency and the date
Restaurant prices differ by city and venue. A converted price is not the bill. Keep the local amount and the date with the observation.