Matching Relational Records. Is It Possible Using Data Minig?

Problem:
I am working on a price comparison system which matches the best prices for a purchase (or an order) from exisiting purchase data.
The order is stored in multiple tables including order details (stores major items purchased: e.g., PC) and order sub-details (optional items purchased with the major items: e.g., speakers, backup device, webcam etc.).
There could be a number of major items in an order and each major item could have multiple related sub items. The other variables that affect the price include trade-ins if any, sales going on at the time of order, number of units etc.

Now, for any new configuration (major items/related sub items), the system should be able to return a list of previous purchases made with similar configurations, and similar variables (quatities, trade-ins etc). Even if the same model is not present, similar pcs by the same vendor should be considered. etc etc.

Questions:
Is this possible using Data mining?
If yes, which algorithm is recommended?

Also, can I assign/modify any kind of weights to certain variables (if same model: .6 ; if same model not available but pcs made by same manufacturer available: .3 ; by other manufacturers: .1)?

Any help will be greatly appreciated.

Thanks,
Jojy