Bottom line...they're charging for their time and expertise. Check to see if the property has been surveyed before and use those folks as they should have the information on record and will only have to go back to the land and make sure nothing has changed (roads moved, water eroded lake front property, etc.) Can cost as little as 300-500 in a small sub-division up to several thousand for large pieces of land.
Ask the previous owners if they have a certified survey or ILC from their purchase, but I'd still recommend that you have your own completed since encroachments, fence lines, etc.... do change over time.
If you're working with a broker they should have a local surveyors information.