As people that live here know the minibus visa run is a nightmare to do. I did it once from here and vowed never again. I now do it myself or with some others if the need to go at the same time or thereabouts. a breakdown of the costs is here
car hire - 2 days with full insurance for a Toyota Soprtrider 4 X 4 7 seater 3000 Baht
ferry crossing - return via the Raja ferry as you can book your return ticket when you leave as it saves having to queue on the way back 1000 Baht
Fuel there and back - The car comes with a full tank and filling it up at the gas station near the ferry on the way back was just under 2000 Baht.
I have a slow drive down. do the visa run with a stop off at the duty free shop and then book a nice hotel in Sadao at 1000 a night. You can get them from 500 Baht.
So a nice leisurely drive down and a night out and back with a new stamp for
7000 Baht
If you breakdown the cost of just getting there and back and you can find 2 - 3 people to go with you it is for nothing.