What is the tax price on an iPhone 5C based on?

I'm looking to buy a 32GB iPhone 5c at Best Buy. I've heard that the tax price can be based on either the sales price with an upgrade ($200) OR the unlocked price (which is $819 at bestbuy). So, which one is it based on? I live in Southern California, and tax is 8%, if that helps.

Added (1). I do have an upgrade with verizon, by the way. So the price would be $200 for me, I just want to know the tax price (~$16 vs ~$65).

In most states (California for example) it is based on the full price of the phone so here in California this is $600 full price with 10% tax so $60 tax. Sometimes they will pay the tax to get you on a plan but whether they pay or you pay, the government will get their $60.

If your contract is over and you are purchasing the phone at $200 (renewing your 2year contract) so the sales tax is based on that price. However if you are still on your contract and you purchase a new phone then you are paying the full cost price with the sales taxes on that price.

The taxes are more based on location/local laws than prices of the product.

For example a 32GB 5s on contract will cost $299 + 8% tax. An unlocked one would cost $749 + 8% tax. In fact anything sold in CA would come with that 8% add on to the stated price.

So using your case, the 32GB 5c:
$199 + $15.92 = $214.92 (contract)
$649 + $51.92 = $700.92 (unlocked)

FYI: Apple sells the 32GB iPhone 5c for $649
http://store.apple.com/...e/iphone5c
so that $819 price at Best Buy sounds a lot higher than it should.