Aluminum handlebars have quite a range of prices and weights,
depending on whether your priority is reducing the overall weight
of your bike, or conserving dollars. Balancing those two issues
will be partly a function of the type of cycling you insist on
doing, and how big your bank account is!
For the casual road rider it makes little sense on spending big
bucks, probably in the neighbourhood of $100. for a aircraft grade
aluminum handlebar that offers not only the lowest weight, but
also the greatest strength. The weight reduction, relative to
other more significant bike parts (like your frame) will be somewhat
irrelevant, and you may never be pushing your bike to the handlebar's
physical limits, thus a slightly heavier-walled, aluminum 2014-T6
bar for $20. may work perfectly.
On the otherhand if you insist on pushing the limits on steep
climbs the overall strength may be significant. If your passion
is to road race, keeping the weight down maybe important if you
are to have any success... in either case weight and strength
will be something you will want to consider. Spending $100. for
a bike handle bar in either of these cases is not unheard of.
Weight: The overall weight varies significantly both based
on the design and also the aluminum alloy used. Obviously straight
bars will be inherently lighter then a drop or riser bar. Lower
grade aluminum alloy bars are typically heavier then either a
6000 or 7000 grade, not because the material is of a higher density
but rather the necessity to increase tube wall thickness to compensate
for lower strength and yet still achieve acceptable performance.
The higher grade "7000" series aircraft grade aluminum
alloy will typically have a greater strength to weight ratio then
a 6061 aluminum, and the 6061 likewise will have a better ratio
then the 2014 aluminum .... but all of these alloys can produce
a good performance handlebar, albeit at different weights and
prices. As suggested earlier the 2014 version will have thicker
tube walls to achieve the performance of a 7000 series model,
but will definitely be heavier.
As an example, I recently searched the Internet for an Easton
6061 aluminum road bar and it was weighing in at about 280 g.
and $50. versus a Deda 7075-T6 (ie. aircraft grade) at $75.00
and 215 grams. Usually the price-weight ratio can be used as a
general gauge of the grade of aluminum used in its construction.

Easton A30 Aluminum Road Bar
Be sure to ask if the handlebar has been anodized, as this process
will help significantly in corrosion resistance.
Aluminum bars appear to be relatively easy to find in all tube
diameters from 25.4, 26 and the oversized handlebar at 31.8mm
with typically a thicker walled aluminum tube to give a stiffer
ride. Many have grooves built into the design for hiding your
cables.
Warranty: From what I have seen around, most aluminum
handle bars have at best a 5 year warranty, but most bars have
no warranty at all.
Remember that aluminum if abused can fracture (I guess this is
why the warranties are not so exciting) so if you crash, before
you take the next ride be sure to inspect your handle bars carefully
as small fractures can spell big trouble, at the most critical
times!
Related Articles:
Bicycle Handlebars
Designs: road vs mountain biking
Features
to Invest In
Carbon
Fiber Handlebars
Titanium
Handlebars
Other Articles of Interest:
The Anodizing Process: