The premium on a home is usually based on the location and condition of the home. If the location is great but the home is in poor condition - probably won't bring as much money.
Same if the the home is in great condition, but the location is poor - won't bring as much on the market.
When purchasing a home, I think the location should be the prime concern. Unless the home is in really poor condition, it's easier to fix up a home than it would be to fix up a undesireable location.
The premium you pay for a home can vary from property to property. I wouldn't say there's an average but you can have an agent provide you with Comp's for the area of interest to see the price differences.