I am 61, retired and getting CPP, and could start drawing another small pension. Both pensions are less than $12K per year.
RRSP is significant, and provides $30-40K per year and other investments provide $3k per year, and the balance comes from draw down of savings. The RRSP is being depleted faster than it is growing at this withdrawal rate.
What reasoning could justify a 40% - 50% tax rate?
Why
Defined Benefit pension plans (public sector and some private sector as well) can pay a pension that is upto 70% (some as high as 80% I believe) of the employee's employment income. In those cases, if someone is making say $80K a year, their pension could be at least $56K/year (likely higher with indexing).
In such cases, any RRSP withdrawals will be at the marginal tax rate. So that first $ of RSP withdrawal will be taxed at over 31% in ON & AB, and as high as slightly over 38% in QC. This is already much higher than the 21 or 23% tax rate that "the system" would use.
As your annual RRSP withdrawals grow (forced once you hit 71 and have minimum RRIF withdrawals), you could easily hit marginal rates of greater than 40%. For example, that person getting $56K in pension, if he/she withdraws another $34K from their RRSP, the tax rate on the last $100 would be around 43% in most provinces and as high as 45.7% in QC.
So it's not unreasonable that the overall tax rate that would apply to all RSP withdrawals would be in the high 30s or 40s. Perhaps even higher for really high income folks that make in excess of $100K and will therefore be eligible for annual pensions of $70K or higher.
That said, most people either have large pensions (because they worked all their lives at the same employer) and thus low RRSP room and hence smaller RRSPs or have very minimal pensions (CPP only perhaps) and large RRSPs. But there are cases of inbetweeners that may have worked in a non-pension place for several years at the start of their career building up half decent RRSPs and still having enough years of employment at pensionable employers to qualify for full pension. Its for these folks that I believe the higher net RRSP tax rate makes sense.