its not that hard just depends what query you run and how you sort the data is up to you
if your using phpMyAdmin you can sort the data how you want in there and it will show you the php qry
so like:
$result = mysql_query("SELECT * FROM database_table_name WHERE category = 'Category_Name' ORDER BY price desc LIMIT 0, 30") or die("Database Error" . mysql_error());
would get the data for all products in the table called "database_table_name" if the category of the product is "Category_Name" and sort the data by the field called price descending (alternative is asc - ascending) and the limit will only get 30 results.
then do a while statement to loop through and echo out what you want
while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) {
echo "$row[product_name]<br>";
}
that would just print out 30 of the product names (presuming you have a field called product_name) from category Category_Name with the highest prices.
loads of different ways to display the data between the while statement and lots of different data you can return with the $result depending on what you want
and thats the last bit of help im giving this year
or 
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