Generally, Coron scuba diving prices are no more expensive than other parts of the Philippines.
However, it’s worth noting that when wreck diving, because the boat has to travel to dive sites for up to an hour, it doesn’t return to the port until completing 3 dives so unless you wanna spend a tedious hour sitting around on the boat, that’s how many you’ll pay for. If I recall correctly, the price of 3 dives is around the 4000 PHP / $72 mark.
The Dugong diving is indeed expensive; 10,000 PHP / $180 for a day of two dives.