If memory serves, I think the cup was somewhere around $16 or so. I know that I didn't do an optimal job packing the cup with bricks (you can fit a lot more in if you take the time to actually stack the bricks together). I didn't do that - I just dumped stuff in until I ran out of room.
I'm such a novice, huh?!
Anyhow, the real question is: What did I manage to fit into my cup?
To start, a whole bunch of 2x4 bricks. 47 bricks in total including 12 red, 16 tan, 10 light blue, and 9 green. It was probably a rookie move to grab so many basic bricks - I could have acquired those in one of the prepacked Classic branded box sets at my local Wal-Mart. I am happy with the green and tan bricks though - I have very few of them!
I also went pretty have with various sized plates including 9 2x6 brown plates, 8 4x4 green plates, 4 4x6 yellow plates, and 7 4x6 blue plates. That's a total of 28 fairly large plates.
Next, I tried to "fill in" some of the spaces in the cup with a bunch of smaller stuff from the wall. Included in that bundle was a ton of 1x2 purple pieces (36 in total), some 1x2 white jumpers (15), some white 1x2 cheese slopes (13), some 1x4 white plates (11), some 2x2 white slopes (13 - 2 of which had printing on them). I also picked up 3 axle pieces and 5 of the black side pieces (which I don't know their "official" name).
So far, not so bad - but there's more!
The next batch consists of 20 tan pieces with side studs, a single 2x4 green plate (wish I had picked up more of these), and 46 1x1 round bright green studs. I also picked up 7 flower stems though somehow I neglected to grab any flower pieces!! The best of the entire wall (in my opinion) was the final two pieces - the three piece plants and the white picket fences. I picked up 12 of the fences and 41 of the plants.
All told, I managed to grab 298 pieces for about $16. That comes out to a bit over 5 cents per piece which is certainly better than most "packaged" LEGO sets. Of course, those numbers are a bit inflated since I had so many of the 1x1 round studs...
I guess the real value in the Pick-a-Brick wall is that you get to pick exactly what you want. The downside is that the wall is most definitely limited (I know that I wished there was a greater selection of parts type in a single color of MOCs). Even so, I had a lot of fun at the wall - and yes, I'd do it again given the chance (especially for more plant pieces)!