Camel Drivers

Aad and Aalok were camel-drivers and one day they decided to quit their job. They wanted to become shepherds. So they went to the market and sold all their camels. The amount of money (dinars) they received for each camel was the same as the total number of camels they owned. With that money they bought as many sheep as possible, 10 dinars per sheep. They still had some money left, and for that sum of money they bought a goat.

On their way home they got into a fight and decided to split up. When they divided the flock, there was still one sheep left. So Aalok said to Aad, "I take the last sheep and you can get the goat". "That's not fair," said Aad, "a goat costs less than a sheep". "OK," Aalok said, "then I will give you one of my dogs and then we are even". And Aad agreed.

How much did the dog cost?