Exactly. Tax collective simply is not feasible given the fact that you`d have double the base pr that a normal TAX terran would have at the same tax income. You might say it takes TWICE the population to get the same tax income as a terran.
Now couple this with the fact that collective empires do NOT do well with a high base pr (unless you`re skilled) and no exploring, and you`ve got one HARD path. Oh and don`t forget that high food prices suck too.
Now, if you manage to capture a 20k land c2 or a great c3, you can actually use it to make your cash instead of being forced to plunder it for as much plunder money you can get it for. Then again, high base PR especially sucks for collective on turnbased servers, although it`s not as bad as it used to be before the update.
But hey, if you can succeed as a tax collective and not die then I applaud you.