Dust on compact camera sensor?

I believe I've got dust on the sensor of my Nikon P300 compact camera.
There appears to be a grey dust spot and it can be clearly seen on the pictures taken.
The dust spot appears smaller when zooming and larger at the wide end.
Is this a common occurence for compact cameras and how much would it cost to have the sensor cleaned? Camera has always been used under 'normal' circumstances.

I have 5 compact cameras with no dust spots
your normal and my normal must be different
ask the camera store how much