Puzzle games:Very puzzling prices

If you have a keen eye, you will notice that puzzle games are constantly flooding the portable consoles, especially the DS, nowdays. There is a wide variety of them, ranging from PSP's Lumines (see picture), to DS's Sudoku Grindmaster, to the innovative Electroplankton, to the latest game, Magnetica. There is something for everyone! But as puzzling as the puzzles in the games may be, the puzzling thing is that the prices of these games are just as puzzling! My question is:Are the puzzle games really worth the bucks? Afterall, there are many puzzle game offerings from various online game websites and you can play them for free! Many puzzle games that I have encountered in the stores is expensive (for a puzzle game), save for games like DS's Brain Age and Big Brain Academy, both of which can be picked out from the budget room. So, my second question is:How long can a puzzle game sustain your attention? Probably no longer than 4 hours, I think. The puzzle game genre was never successful in escaping the notorious fact that they are lacking in content. No matter how many different modes a puzzle game may have, the situation will still remain unchanged. Let's take the game I mentioned earlier, Sudoku Grindmaster, for an example. Oh my, it has never crossed my mind that playing Sudoku was to be such an expensive hobby, considering the fact that the DS game is selling for 20 bucks. You can play Sudoku on www.miniclip.com for free and on paper for a fraction of the cost! Okay, let's have another game. Whac-A-Mole for the DS. Yeah, you guessed it right! The game is mainly about -- whacking moles! But the action is missing, well, yeah, so is my money, after paying. I suggest that you head down to the arcade right away and have a real 'Whac-A-Mole' experience and yet again, this method is less costly. However, the theory of 'costly puzzle games' cannot be applied to some others. If you have played Geometry Wars for the Xbox 360, you would have understood. By the way, the game can be found on Xbox Live Arcade and it can be bought with only 400 Microsoft points! Or if you do not have that amount, just pay -- the price is reasonable. Yes, the game is cheap, but quality is not compromised. Yes, the game is simple, but it is fun. Hey, wait, do you remember playing Tetris? I used to play it in the earlier days, but when I play it now, it just feels so outdated and I can only recall playing the game with nostalgic pleasure. Anyway, cheap and fun -- that is my hope, my vision for puzzle games. And I really hope it will come true one day, because I am sick of overpriced puzzle games.