But beware! This NPC is always drunk so it is highly likely he will take you to wrong places occasionally. Bringing a Dwarven Ring in your backpack makes him take you to the right spot but you lose the ring. When the Dwarven Ring is used you also don't have to pay the 50 gold.
There are two ways to prevent him from taking a Dwarven Ring you may be carrying:
The first and easiest way is to just tell him "no" when he offers to take it. (Note: this is the only way to prevent him from taking a Dwarven Ring if you have more than one with you).
The second way, if you carry just a single Dwarven Ring, is to equip it in your ring slot. He won't take it then.