value of perfect information

the following example states ” in a concert theatre with uncertain audience of 300 400 and 500 people with associated probabilities of 0.50, 0.30 and 0.20, price per ticket is 25 per person.
Additional contribution is to be earned from customers at the level of 3, 5 and 10 with corresponding p of 0.3. 0.5 and 0.20. Fixed fee for the concerts is 10.000.

the table of profits is as follows:

fee Demand
300 400 500
3 (1600) 1200 4000

5 (1000) 1200 4000

10 500 4000 7500

What is the value of perfect info. In the answer it says 490 as it is the value of loss multiplied by joint probabilities. I thought it was zero, as without perfect info
highest ev corresponds to contribution of 10 and is 590. The same would be with perfect info. under each demand column, as demand would be predicted we could choose
for 300 demand return of 500, for 400 demand return of 4000 and for 500 demand return of 7500, the ev would be the same 590. If perfect info does not change the value of decision, it s value is zero.

Thanks.