4th & Dragon : Dungeons and Dragons...and stuff

Ok my question is what is the price for basic building materials. I mean like stone, mortar, and wood. Anyone have an idea?

The stronghold builders guide has a very very complete set of rules for building well buildings.
Including rules as to how different magic can speed up production time as well as cost.

D&D doesn’t really deal in basic costs for materials just the finished product.

The better way would be to assume a percentage of income cost and a harvest/labour cost then meld them based on the situation.  (ie. a forest is nearby and free to harvest then it has a labour cost only as the equipment to mill is cheap and easy for any smith to make.  but on the other hand if it is in a city then you have to assume that people are building in relation to income and that will tell the market how much it costs for everything)

If you mean for you own deck out back, I build houses now so I can get a pretty accurate cost expectation to you.

The most complete system I know for handling construction costs in D&D is in Magical Medevial Society: Western Europe, Appendix IV.  It covers everything from structure type to height to material to carriage to magic.