select max(final_price), (select products_tax_class_id from ... where final_price = max(final_price)),
min(final_price), (select products_tax_class_id from ... where final_price = min(final_price))
from ...
select max(final_price), (select products_tax_class_id from ... where final_price = max(final_price)),
min(final_price), (select products_tax_class_id from ... where final_price = min(final_price))
from ...