I’ve never seen that even before the pandemic. 1.5x-2x is normal for all the usual reasons a contractor cost more. Taxes, benefits, agency that needs a margin, etc.
I’m guessing if you’ve seen that is hyper localized to some place/issue.
1.5x isn't a real increase in staff rates if all it accounts for is taxes and benefits that the employer covers for regular employees anyway. It is like certain government employees who complain about being paid too little when the actual cost of their compensation in many cases is through the roof.
The situation is so bad that regulation or standard practices encouraging employers to document compensation figures instead of quasi-mythical salary figures would do a lot of good to reduce confusion in this area.
All in, it's still averages about 20-30% more expensive in a normal operating environment (before pandemic and all the subsequent issues). This is significant on the largest expense line item and considering it's controllable to a degree.