[PC] Steam - Fallout: New Vegas Ultimate Edition - €3.40 Euro (~ $4.95 AUD) - Gamesplanet.de

This might have been a little bit cheaper before but right now this is the cheapest for the Ultimate Edition.
I am not sure if a VPN with exit Germany is required as I have not tried it.
Update: According to Rozza NO VPN IS REQUIRED. Enjoy.

The normal version is 2.38 Euro (~$3.47)

The Ultimate Version includes all DLC so maybe worth splashing out the extra $1.50.

From the Steam page:

"Welcome Back to New Vegas!

With the introduction of the Ultimate Edition, Bethesda Softworks offers you the chance to double-down and get the complete package of New Vegas fun. For the first time in one package, you can get all the Fallout: New Vegas content including the full suite of highly acclaimed add-on content: Dead Money, Honest Hearts, Old World Blues and Lonesome Road. To sweeten the pot, you’ll be armed with the latest cache of unique weapons, ammo types and recipes from the most recent add-on packs: Courier’s Stash and Gun Runners Arsenal. Whether you’re a seasoned explorer of the Mojave or playing the game for the first time, you’ll find there are more friends and enemies to make, more consequences to your actions and more opportunities to live in glory or infamy throughout the Wasteland. The choices you make will be as crucial to your survival as ever.

Beyond the Wasteland: The world of New Vegas is more expansive than ever. Each new distinct area presents a fresh set of branching-quests, remarkable personalities and more chances to play the Savior or the Pariah to the natives of New Vegas.
Shiny New Toys: Each add-on pack increases the mountain of armaments already at your disposal. Whether you’re an in-your-face brawler or a long-range gunner, weapons such as the Two-Step Goodbye (unique ballistic fists) or Sleepytime (a handy 10mm Sub-Machinegun) will give that warmonger in you a chance to flex your ammo-filled muscles.
Room to Grow: With each of the four main add-on packs, the maximum levelcap is increased by 5 levels, ultimately raising the ceiling to Level 50.

Dead Money: Lured into a trap masquerading as the Sierra Madre Casino, you are thrown into a high stakes game where you’ll have to work with three other lost souls if you want to survive.
Honest Hearts: An expedition into Utah’s Zion National Park goes horribly wrong and you become embroiled in a war between tribes and put into a conflict between a New Canaanite missionary and the mysterious Burning Man.
Old World Blues: Transported to the Big MT research crater, you are enlisted by the Think Tank to save them from their own science experiments that have gone horribly out of control.
Lonesome Road: Ulysses, the original Courier Six, contacts you and promises to answer why he refused to deliver the Platinum Chip at the start of Fallout: New Vegas, but only if you make one last journey into the treacherous canyons of the Divide. "