Do your local regulations permit this? A lot of jurisdictions won't permit that much impermeable surface.

It can be very unpleasant sitting in an all-paved area even in mild weather. Heat is reflected from the pavement making the area a lot hotter. Try sitting on your paved driveway on a sunny day to see what it can feel like before paving over your entire back yard.

^^ +1

They are also material-dependent - gravel or DG is cheaper than pavers/concrete slab and that is cheaper than natural stone.

The answers to questions about how much landscape things cost depend on too many factors including how much of the work you do vs having it done, and how much demolition must be done first, in addition to what has already been mentioned. An area to entertain in in the backyard might start at a few thousand $ for something basic, but there is no upward limit on what one could spend. Outdoor kitchens, water features, shade structures, fog systems, music -- it goes on and on -- can cost in the tens of thousands of $ for yards that are not particularly huge. You might consider what you can budget and get a gut reaction to if people think it is reasonable for what you want. That's a somewhat less open-ended question.

We try to give prospective clients starting ranges, so that they can know if they're even in the ballpark. We don't estimate the actual job by the square foot, but we can look at historical prices to start the conversation. For example, we let them know that in our area, paver patios generally start at $20-30 per sq ft (not including site prep, demo, drainage work, and grading). Even in 2017 we're seeing the occasional person who thought they'd get it done for $5/sq ft. I always hate being the one to pop that bubble, but it's a necessary evil.

The OP should start with a landscape designer. It's impossible to tell from those photo mockups how big anything is, which means that if those are used to solicit #s - they're going to be all over the map.