1. A method of suggesting an auction bid modifier comprising: retrieving, by one or more hardware processors from one or more databases stored in memory, a likelihood of a visit to a physical establishment resulting in a completed transaction at the physical establishment; retrieving, by the one or more hardware processors from the one or more databases stored in memory, an average transaction amount for the physical establishment; retrieving, by the one or more hardware processors from the one or more databases stored in memory, an expected return on investment (ROI) for a transaction made at the physical establishment that resulted from placement of third-party content, the expected ROI based on a cost associated with the placement of the third-party content; receiving, by the one or more processors, a maximum travel value associated with the physical establishment; modeling a probability of a visit to the physical establishment based on the received maximum travel value for the physical establishment wherein the probability of the visit to the physical establishment comprises an exponential decay function having a minimum probability at the maximum travel value: receiving, by the one or more hardware processors, a base bid amount for a content auction; determining, by the one or more hardware processors, a travel value for the physical establishment, the travel value quantifying a relationship between a location of a client device and a location of the physical establishment: determining, by the one or more hardware processors, an auction bid modifier based on the modeled probability of the visit to the physical establishment, the maximum travel value, the travel value and by dividing a first product of the average transaction amount likelihood of the visit resulting in the completed transaction by a second product of the ROI and the base bid amount; selecting, by the one or more hardware processors via a real-time content auction in response to a request from a client device, an advertisement for the physical establishment based on the auction bid modifier; and providing, by the one more hardware processors via a network, the selected advertisement to the client device to cause the client device to render the selected advertisement on a display device.