Public comments were made on Monday during a state Senate transportation committee.
The outcry over higher car tab taxes to pay for the light rail on Thursday led Sound Transit's board to consider other options for collecting that revenue, but even the board chair acknowledged he wasn't sure what those options might be.
Some car owners are upset by higher vehicle licensing bills, after voters passed the $54 billion Sound Transit 3 expansion in November.
The valuation system Sound Transit uses has been in place since voters passed the first light rail measure in 1996.
It doesn't depreciate the value of cars nearly as fast as the Kelley Blue Book calculation, or even an alternative system developed by the state in 2006.
Sound Transit expects to move to that newer state system in 2028, once the first motor vehicle excise tax expires from the 1996 ballot measure.
In the meantime, the agency has planned to stick with the current valuation process, which it says values 60 percent of vehicles in the taxing district at $10,000 or less.
"I've got neighbors who are seeing $300, $400 more on their tabs each year,” said State Rep. Mark Harmsworth, (R) Mill Creek, who is a sponsor of a state bill aiming to reduce fees.
Republicans in the state Senate are trying to block Sound Transit from receiving any car tab revenue unless it changes to the 2006 system right away, a move the agency says would cost it $6 billion.
Two billion dollars of the loss would be in direct revenue, and $4 billion would be in higher debt service costs.