Initial investment is after tax but you get a tax refund so in effect you lent out money to the government interest free. The government thanks you for that.But the initial investment is after tax, and accumulation within the RRSP is tax free, yes until withdrawn but can time withdrawls based on need and tax effect.
You pay now or pay later and you're actually paying more later if you have investment growth. It's not tax free in an RRSP