Here's a passage form the book I am currently reading which explains it quite well.
Bones are Forever by Kathy Reichs
The book is fiction and the story set in Alaska.
All place names are probably fictional, I haven't checked.
Although I've read that Kathy Reichs does research her subjects fairly extensively, so perhaps they are real place names.
The passage I've reprinted here is a conversation between two people.
"I've learned why bling is so bloody expensive.
First you have to find the diamonds. Then you have to do a feasibility study to determine how much the mine will cost and how to build it. Then there's the red tape: environmental agreements, land-use permits, water licenses, impact-benefit agreements, socioeconomic agreements.
Approval involves dealing with Federal, territorial and aboriginal governments, regulatory agencies, land owners-everyone from the local farmer right up to the Pope.
Then you have to build the mine, which, in this climate, is a nightmare. The sites are so isolated that all personnel and supplies have to be flown in, or transported over winter roads."
"Ice road truckers!"
"Do you know what it costs to operate an ice road?"
"I do not."
"Lupin runs for almost six hundred kilometers.......Construction and maintenance cost roughly six point five million dollars annually...... And the ice roads are only open maybe ten weeks a year."
"That's just one budget item. Landing strips, power stations, machine shops, sewage and waste disposal, water treatment plants, telephone networks, storage buildings, offices, processing plants. and the workers can't exactly drive home each night. The mines have to provide housing, food, recreational facilities. A Lot of the miners work two-week rotations. That's a long time to have nothing to do.......Ekati construction cost nine hundred million dollars. Diavik cost one point three billion-that's billion- dollars."
So there's at least part of the reason .
All of the initial cost must be recovered and then the companies wish to see a profit too.
Now you know why those sparkly little rocks cost more than your house. Or maybe just more than your car.
Thank you, Kathy Reichs for this information.