Top Drives - Is Double Rewards in Clubs worth it?

 Short answer; No, unless you play a clubs a lot.

The following image is from Top Dives and shows the drop rates of a ceramic pack.

Drop Rates of Ceramic Car Pack

 

Drop Rates of Carbon Fibre Pack

These maths are going to be rough, you have two options to get an ultra rare Car

1. Buy a Carbon Fibre Pack costs 1,499 gold to get a guaranteed ultra rare. 
2. Buy 6 ceramic packs, statistically you should get an ultra rare.

Six ceramics will cost you $192,000, so we could argue that gold is worth 1,499 - 192,000, so Top Dives exchange rate of:-

1g = $128

So the cost of getting double rewards on clubs is $63,872, you will need to do a lot of racing in Top Drives Clubs to make that much!

The numbers get worse if you factor in increased chances of epic or legendary cars, thought I would do the math from legendary point of view.

You have two options to get a legendary car 

1. Buy 34 Carbon Fibre Pack costs 50,966 gold you should get a legendary car
2. Buy 154 ceramic packs, $4.89m statistically you should get a legendary car

1g = $95