If you bring three people's luggage, then you have to pay more for the free part of the other two people than the three people.

That is, the other two people need to pay 8-4=4 yuan for their free luggage.

1 person free luggage. If you pay, you need to pay 4÷2=2 yuan.

Then if all three people pay for free luggage, they should pay 2×3=6 yuan.

That is, if the luggage is paid in full, it should be minus 4+6= 10 yuan, which is 150 kg.

So each yuan can carry 150÷ 10= 15 yuan.

Each person can carry free baggage worth 2 yuan, that is, 15× 2 = 30kg.