" the XT-E LED delivers up to 148 lumens and 148 lumens per watt in cool white (6000 K) or
up to 114 lumens and 114 lumens per watt in warm white (3000 K), both at 350 mA, 85°C."
'UP TO ...' is a dead giveaway that most of the production units are way below the quoted number or the wording would be 'MINIMUM ...'.
'114 lumens per watt in warm white (3000 K)' Most A style LED light bulbs sold in North America is warm white/soft white to closely match incandescent tints. So you are down to 114 LED lumens per watt
or less.
Now your power in is 115VAC. There are losses converting it to the required DC. This is made worse by the requirement that electrical equipment needs to have a power factor of 0.9 or better in North America. Figure in another 15-25 % loss bringing your lumens per watt down below 97 lpw.
Then comes your optical losses. The venerable Maglite had been tested in both incan and LED versions and only 65% of the LED lumens come out the front. While LED A style bulbs are not as bad a loss of another 10% would bring lpw below 90. That is the best case.
So much for an XT-E bulb producing 140 lpw.
BTW for maximum efficiency LEDs and their electronics need to keep cool. So a big heatsink is a must. Take a look at the SIZE of Cree's prototype light bulb:
http://www.youtube.com/watch?v=rWx_2fqhzOQ
The most efficient bulb on sale right now is the Philips L-prize winner. MSRP is $60 though you can get it for $50. The bulb is using high efficiency cool white mixed with red LEDs to get to 94 lpw. The extra complexity means it won't go under $10 anytime soon.
http://www.candlepowerforums.com/vb/showthread.php?334754-Philips-Award-Winning-LED-Bulb-Review
Keep an eye out for coupons for this bulb in your electricity bill. Should bring the prize down to $22 to $25.