A wide range of tile colours and profiles is available. Concrete tiles cost from approximately $65 per square metre. Quality French clay tiles start from around $180 to $240 per square metre with lead flashings.
The market value, assessed value and taxable value of your house are often nothing alike. The market value is what your house would sell for in the current market. The assessed value is what your county tax assessor reports the house is worth for purposes of calculating your property tax bill. Taxable value is the figure you actually pay tax on.
In my county they take the lower of real market value or a maximum assessed value. Voters in my state also instituted a law that caps the growth of property taxes to 3% a year. I highly recommend researching how your tax authority assesses values.