Taxes in California are for now determined by THE SALE PRICE. Howard Jarvis got a proposition passed by the electorate in 1978 known as PROPOSITION 13. It holds all property taxes to 1% of the value of the sale price of the property.
It was designed to protect the elderly from losing their homes, as the values increased and their income decreased. Most counties, including Los Angeles allow sellers to relocate within the county and keep their original tax base. Some counties around California co-operate and allow people to move from county to county and move their tax base.
The tax rate has been adjusted to 1.25% so that the county are able to collect a more dollars than originally mandated. The county ASSESSED value normally has no relationship to the actual tax owed.
It is important when buying a new home to negotiate the very best possible price for purchase, as that does determine what the tax will be and of course that's how you as a buyer get the best possibility for an increased return on your real estate investment.
Always use your own agent and choose an agent who is a negotiation expert!