I think they are right. Having picnic can make us happy, relaxed, cheerful. Besides that, travel or having picnic we can see nature, forest, jungle, and have funwith local people. We will know also the local people's food, drinks, behaviour, norma, or culture. It will become the new things for us.
But having a picnic spends a lot of money. Yes, you are right there, anyway everything you do you have to spend your money, none free in the world. It is better to travel to the world or to other places in your country rather than you save your money in the bank, even though your deposit rate increase, however you will never know how balinese people's life, how korean eats, how qatarian greets her/his friends, how russian people enjoy their dinner.
Travelling can broaden your mind also, you will know how people of a country make bread, cake, meat ball, or drinks, such as to make milk, banana milk, wine, and coffe. Well, for example, you can see also, the balinese creates statue, painting art, tatoo. Then you travel also to Beijing, you will see chinese play kungfu, and you will see the chinese great wall.So through travelling , your mind will be broadened.
Making a picnic in your life is full of happiness, loose depress. Surely, I tell you do a picnic changes your your brain be happy, fresh, because what you saw in the tourist objects makes you smile, laugh, surprised, as it is different from your country.
I suggest you , do have a picnic abroad to your neighbour village, eventhough to Russia.