How much more of your time is actually required to e-file rather than paper file?  I think it involves less time.  Do you manually prepare your tax returns?  I no longer have #2 pencils with erasers.

Paper filing requires you to make additional paper copies, which costs you more in supplies in addition to additional postage fees for you and your client. Then you need to staple those little W2's to the return (make sure you use the correct copy of the W-2), file form 8948, prepare vouchers to make payments (Personally I don't care how they wish to pay).

Then, your counting on the USPS...you know the entity that loses $12 billion dollars a year.  Armed IRS agents? (Isn't Biden gone?).  I never heard of unannounced 8879 inspections happening but mail does get lost.