I will also voice my opinion regarding TMs as Game Corner prizes. Like others have already suggested, I believe that for TM prizes, especially those in the higher tiers, players should get more than 1 of that TM as a prize. Given how learned TMs are lost when moveset changes are made via the Playerdex, how often people are changing movesets on their Pokemon in order to experiment with new combinations, and how long it will take to get vouchers, having only 1 of a Game Corner TM can put the player in a real bind. I would recommend at least 3 of the prize TM be given to the player. Seeing as how some prizes are an egg + an evolution item, I see no problem with distributing multiple TMs at once. I've given an example scenario below that has already crossed my mind as being troubling in the near future.
Let's say I purchase a Focus Blast TM using 7 vouchers, and now I have no vouchers left. This means it could be months before I can purchase another Focus Blast TM again. I teach Focus Blast to my Alakazam, which also has Future Sight, Calm Mind and Shadow Ball in its moveset. However, one day I learn that Future Sight has been fixed and now has a charge turn. Obviously, I will want to replace Future Sight with Psychic. However, doing so requires that I go to the Playerdex, meaning that I will lose both Shadow Ball and Focus Blast. Luckily, I have spare Shadow Ball TMs, but now I no longer have Focus Blast, a key move for Alakazam. As such, now I need to wait for months before I can use my Alakazam at its peak potential in battle again.
This is just one scenario. I'm sure there are others that could arise and frustrate players, even if it's simply teaching the TM to the wrong Pokemon or forgetting the wrong move in place of a TM. Things to consider.
Let's say I purchase a Focus Blast TM using 7 vouchers, and now I have no vouchers left. This means it could be months before I can purchase another Focus Blast TM again. I teach Focus Blast to my Alakazam, which also has Future Sight, Calm Mind and Shadow Ball in its moveset. However, one day I learn that Future Sight has been fixed and now has a charge turn. Obviously, I will want to replace Future Sight with Psychic. However, doing so requires that I go to the Playerdex, meaning that I will lose both Shadow Ball and Focus Blast. Luckily, I have spare Shadow Ball TMs, but now I no longer have Focus Blast, a key move for Alakazam. As such, now I need to wait for months before I can use my Alakazam at its peak potential in battle again.
This is just one scenario. I'm sure there are others that could arise and frustrate players, even if it's simply teaching the TM to the wrong Pokemon or forgetting the wrong move in place of a TM. Things to consider.