From memory, the 4473 went from 5 to 4 lines for firearms in 2016. It lowered from 4 to 3 lines in 2023. There is still an additional form you can use for multiple transfers, 5300.9A
Here, $25 is a standard small shop fee and the big retailers charge $50-75. No additional fees to the customer beyond the transfer fee. Most will charge per firearm, some charge per 4473 if all 3 guns are delivered in a week's time. I've not seen a FFL fill out a continuation sheet in years, many have said they were not familiar with it.