I don't watch the Food Network, nor do I jump into "challenges" readily. I'm challenged enough, thank you! But I can see how some challenges could be fun, if you like that sort of thing, and as pointed out, clicking on a thread is a choice.
However, there was something very basically wrong with the $5 challenge, and it speaks to the points above about whether a meal for $5 is a useful topic. Yes, plenty of people don't have the luxury of buying whatever strikes their fancy, or are on a tight budget. If we wish to serve that need it can't be a game. Buying all the ingredients for one $5 dinner is in no way a practical solution to eating as well as possible on $15 a day (or something like that.) No one wants to eat badly for $5 a meal. Some people can use help figuring out how to make a week's worth of decent meals for an average of $5 per meal: in other words, how to plan and shop for real value, learning how to cook large amounts at a time, learning to re-purpose leftovers, learning to cook less expensive cuts of meat, etc. Really, like other aspects of cooking, these are skills that go far beyond looking at the price on a package.
So, on the topic of what makes a good challenge, it helps to think it through.