First off, I'm a newbie. Actually I'm more of a "want-to-be-a-newbie" as I haven't started doing anything back country yet (car camping to date). My questions are based off what little knowledge I have gathered so far; I would greatly appreciate any shared wisdom.

For context I'm 23, male, 5'9", 130lb, in reasonable hiking shape, but so far I've only made day trips of maybe 12-15 miles max and limited pack weight in the Colorado Rockies.

What I'm looking for:
-2 Person Tent to share with girlfriend (and while solo) while backpacking in a variety of climates (alpine, desert, jungle, all of it)
-3 Season (down to 25 deg F at the lowest, mostly 40 deg F or warmer)
-Double Layered
-Bathtub floor
-Vestibule space
-Prefer to stay below $200; mostly I figure I'm not experienced enough to know what I really want/need and would rather not shell out a ton on something that may not be what I really like.

Now, a general question on tents, quality and pricing.

What really is the difference between a $100, $200 and $400 tent? As an example...

-$109 on Amazon: Alps Mountaineering Lynx 2: ~5.5lb, 37 ft2 tent, 20 ft2 vestibule, 6" x 20.5" packed
-$219 at REI: REI Half Dome 2 Plus: ~5 lb, 38 ft2 tent, 20 ft2 vestibule, 7" x 21" packed
-$250 at MSR: Elixir 2: ~4.9 lb, 29 ft2 tent, 17.5 ft2 vestibule, 7" x 20" packed
-$400 at MSR: Hubba Hubba NX 2: ~3.5lb, 29 ft2 tent, 17.5 ft2 vestibule, 6" x 18" packed

All have 2 doors and vestibules. The Lynx and Half dome seem near identical but $100 difference in price. The Elixir, however, is roughly the same weight with far less space yet $30 more than the Half Dome and $130 more than the Lynx. Finally the Hubba Hubba is the Elixir except 1.5 lb lighter with a smaller packed size but a whopping $400!

I can chalk some of the price hike up to weight savings/smaller packed size with the Hubba Hubba, but otherwise I'm baffled at the price differences, especially with the Elixir being so small relative to the cheaper two. Is there a huge quality difference between these tents otherwise? Are there small features included in the MSR tents which warrant the price hike?

This is just an example, but I'm trying to understand what exactly separates the expensive tents from the cheap ones, and when (or if) it is really worth the added cost.

Thank you all for your help!