There is not a single site or even multiple sites where the costs will be published. Reason being is that most doctor's practices are private businesses and are not governed by any entity as far as cost is concerned.
From the past experiences of myself and many others the cost for a regular office visit runs $80-$200 depending on the physician. Urgent care visit runs $120-$250 depending on what they had to do, and so on.
Emergency rooms could get a lot more expensive depending on the care that they had to provide you and the hospital you visit.
So if you feel like judging costs of care you should probably start looking at review sites like YELP:
Where cost is mentioned in the reviews.
P.S. Supposedly the new Obamacare webiste is supposed to provide you with that information.