Usually people that still use their legacy mac falls into one of the following two categories:
1) It is their secondary mac and they already have another more modern mac.
2) They use it to run OS9 and other classic apps and games.
If they fall into #1, speed doesn't really matter. They've probably passed it down to their young kids to play educational games, or use it as a jukebox, kitchen mac etc. If the computer dies, they wouldn't been devastated because the computers would've already proven its worth. However, if the OP's old mac dies, it will be a complete waste of money, and he/she will be out of $200 as well as a computer.
If they fall into #2, again, it's often more of a hobby than actual day to day use. They will use apps/OS that are less demanding than the ones that the OP will be using. Having an old computer as your primary computer and run modern apps on it is not the most pleasant experience.
Lastly, there is a difference between using the old mac that you bought 7-9 years ago, and buying a 7-9 year old mac today. It was a wise decision to buy that mac back then, it is not a good decision to buy it now.