The base price shown is for the lowest cost VDO sensor in the list of those available above. The additional cost depending on the type of sensor chosen is shown on this list and is in addition to the base price.
The VDO Pressure Sensors shown above have 2 terminals, one with a 0-5 BAR resistive output, suitable for 5 Bar VDO gauges. (The resistance output is ~10-180 Ohms.) The second terminal is a low pressure warning contact for use with a dashboard warning light. The switch point of the warning contact is shown on the list above for each sensor.
"ER" means "earth return" and means that the sensor is earthed via its thread / engine block (there is no separate insulated connection for earth).
(Insulated Earth Return sensors or sensors with a single output for a gauge are listed on the product page separately.)