Many of us will likely never attempt to do this achievement and will have to settle for the 140/200 due to the extreme length of time doing this would take. Just by doing this for one level, and the easiest level to boot, would take you an hour and a half at 1 minute per game. Now, factor in level 50 alone, which is about 8-10 minutes for wave completion, and you're looking at around 14 hours just to get wave 50 to level 99 alone (and that's with some beefed up power ups and a lot of gems needed). Currently there is only ONE user who has completed this achievement at trueachievements.com, and he would estimate it looks upwards of 300 hours to complete every wave to level 99. Keep in mind that 99 levels*50 waves = 4900 minimum playthroughs.
If you are going for this one, prepare for it to consume a good chunk of your life. If you are brave enough, "MajesticPanda89" over at trueachievements has some good strategies/plans for you, which can be seen here. I won't paste them here so as to steal his solution, and knowing I will never accomplish this, I have no plans on adding my own solution. However, what he suggests is the general plan I would take if attempting this, so head on over to the posted link for help with this pain in the neck achievement.