I can't speak for the EU, but I did live in a Honda for a loooooong time in the US. I kept thinking it would be cheaper because I wouldn't have to pay rent. I'm even eligible for 1/2 price camp spots in federal campgrounds (there are quite literally thousands of campgrounds in this category). Sometimes, I was spending only $4 per night.
However, there are hidden costs you don't think of. For instance, when I added up the $$ for having a tiny cooler for milk, bacon, eggs, and blueberries, @$2 per day for ice, that's $60 a month. Since I didn't have a way to store homemade casseroles and soups, my main meals ended up costing more than they would at home. Laundromats started to add up: $10 per week would be $40 per month.
Cooking fuel costs more than you might imagine, and then fuel is needed to run the lantern.
The toilet might be quite a walk, and if you're in a cheap space, it's likely to be a privy (although these are sometimes better than flush-toilets). You have to buy drinking water, since there's no way to tell if public water is actually potable.
The car needs oil change, maintenance, and new tires to accommodate the extra miles. Driving all those extra miles increases the costs of insurance.
There is specialized equipment. I had this already, but it really adds up: a rain canopy for the picnic table, guy ropes, clothes pins, stove, dish basin, headlamps, batteries, lanterns, sleeping bag....
Federal campgrounds generally don't have wifi, so you have to figure out how to address those needs. How do you entertain yourself? You can buy books. Or you can borrow them from a nearby library, for which you'll need to pay for a card since you're not local. Or—my method—get a library card for the sole purpose of downloading public library books, and since you can only take out 3 at a time (not close to enough for me), you might have to have 2....
Then you need a resettlement kitty for when you have to return to your mundane reality.
God forbid you need healthcare because you tripped on a root in the middle of the night on a nature call.
See what I mean about stuff adding up? True, I've given you US expenses, but my point is that things that don't cost money at home, can cost a lot on the road, and there are many, many, many hidden expenses.
Doing all this in the EU? I can't even imagine being able to afford it. I find the EU very expensive.
And, I'm sorry, but chia seeds would never have fit in my budget.
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PS I highly recommend cooking blueberry pancakes, eggs, and bacon on a picnic table at an interstate rest area, just to see people's faces when they see and sniff the whole layout.
So few people know it's there, and this little thing could save their lives.