1. A method comprising: under control of one or more processors of a computing device, identifying an item offered for sale at an electronic marketplace by an automated agent accessing a web page associated with the electronic marketplace and crawling the web page for identifying information associated with the item, wherein the automated agent comprises instructions stored in memory of the computing device and executable by the one or more processors; identifying a seller of the item by the automated agent crawling the web page for identifying information associated with the seller; extracting offer details associated with the item by the automated agent crawling the web page for the offer details and storing the offer details in a data store; employing, by the automated agent a checkout emulator to: select a first geographic location and a second geographic location; proceed through a first simulated checkout process for the item on the web page up to a point in the first simulated checkout process without acquiring the item, the automated agent specifying the first geographic location as part of the first simulated checkout process; proceed through a second simulated checkout process for the item on the web page up to a point in the second simulated checkout process without acquiring the item, the automated agent specifying the second geographic location as part of the second simulated checkout process; determine a first hidden cost associated with a first transaction for the item, the first hidden cost comprising a first added charge that is included in the first transaction for the item and revealed after the automated agent proceeds through the first simulated checkout process up to the point in the first simulated checkout process; and determine a second hidden cost associated with a second transaction for the item, the second hidden cost comprising a second added charge that is included in the second transaction for the item and revealed after the automated agent proceeds through the second simulated checkout process up to the point in the second simulated checkout process; comparing the first hidden cost and the second hidden cost to a threshold; determining that the first hidden cost or the second hidden cost exceeds the threshold; determining, based at least in part on the first hidden cost or the second hidden cost exceeding the threshold, a frequency at which the seller has provided excessive hidden costs with item offerings; designating a rating for the seller indicative of a reputation of the seller, the rating being based at least in part on the frequency at which the seller has provided the excessive hidden costs; identifying at least one other seller of the item by the automated agent crawling at least one other web page that is offering the item from the at least one other seller; employing, by the automated agent the checkout emulator to: proceed through a third simulated checkout process for the item on the at least one other web page up to a point in the third simulated checkout process without acquiring the item, the automated agent specifying the first geographic location as part of the second simulated checkout process; and determine a third hidden cost associated with a third transaction for the item, the third hidden cost comprising a third added charge that is included in the third transaction for the item and revealed after the automated agent proceeds through the third simulated checkout process up to the point in the third simulated checkout process; comparing the third hidden cost to the threshold; determining that the third hidden cost does not exceed the threshold; determining, based at least in part on the third hidden cost not exceeding the threshold, a frequency at which the at least one other seller has provided excessive hidden costs with item offerings; designating an additional rating for the at least one other seller indicative of a reputation of the at least one other seller, the additional rating being based at least in part on the frequency at which the at least one other seller has provided the excessive hidden costs; storing at least the rating, the first hidden cost, and the second hidden cost in the data store in association with the item and the seller; storing at least the additional rating and the third hidden cost in the data store in association with the item and the at least one other seller; receiving a request, from a user device, to access the web page; determining that the request is associated with the first geographic location; and serving, in response to the request, the web page to the user device, wherein the item, the seller, the rating of the seller, the first hidden cost, the at least one other seller, and the additional rating of the at least one other seller are presented on the web page along with the offer details in an electronic offering of the item.