Unfortunatley.
Currently Scrabster-Stromness is £17.05-£19.90 per adult and £8.60 to £10 per kid, and then an extra £54-60 per standard car and thats a single, so high season (yes its more expensive when the ferry is more full)
the nuclear familly two adults, two kids in a car both ways is £199.80 and you still need to get to scrabster and pay for accomodation the other side.
then as per all outsourcers, everything else is extra.
Pentland ferries get no subsidies and run a cheaper ferry from Gills Bay,
One could only imagine what prices they could charge if they got the subsidies Serco are raking in