Well, a large carrier makes considerably more than $20 a week on it. But using those numbers, it's not as easy as 'just the connection fee plus' a $5 or $10 fee. Most carriers are "self-insured", so to speak, where they foot the bill for repairs on the units, either in-house or by an authorized repair facility. Either way that can be expensive. So money has to be made available for that. Also money needs to be there for replacements.
For a brand new driver with a brand new unit, $35 a week isn't outrageous, since you're literally renting the unit and are not taking any risks for maintenance and repair. However, for a used unit that's long been paid for, the weekly fee should be half, or less.
For a driver who brought his 4-year old unit from Con-Way NOW and has had it in service for more than 4 additional years all without a dime's worth of repairs, the weekly fee should be whatever the carrier pays to Qualcomm for the connection, and not a penny more.
In other words, longevity should be rewarded instead of using it as an easy revenue stream. For the first 2 years (for a new or a used unit, doesn't matter), $35 is fine. But after 2 years the weekly fee should be reduced by half, and then by half again every year after that, to where the contractor pays zero for it after about 6 or 8 years. Once the unit has been paid for, several times over, with additional monies having been collected for maintenance and repairs from that and all units, the price should come down.