How much will it cost to replace traction battery ?

As nobody has responded I thought I would.

I don't own a C and the C/Aqua isn't sold in the UK as we have the locally made Yaris Hybrid.

But Toyota UK indicate on their website that replacement cost of the traction battery starts at £800 which isn't that bad. I guess it gives you a ballpark figure. I'm guessing if you add shipping and labour costs to get a better guess. We now have quite a comprehensive HV battery warranty here, running upto 10 years/unlimited mileage, so it's unlikely most people will need concern themselves with replacement costs. This link confirms the UK costings;

Hybrid Cars FAQ | Frequently Asked Questions | Toyota UK

"It is extremely unlikely that a battery will need replacing. In the unlikely event that the hybrid battery does need to be replaced and the warranty has expired, the cost is approximately £800. An annual Hybrid Health Check at a Toyota Dealer is the best way to ensure you are safeguarding the health of your vehicle for years to come."

Hope that puts your mind at rest.