First of all, private cars with less than 7 seats are not allowed to carry luggage on the roof and will be fined.
Private cars with less than 7 seats in Tibet are not allowed to carry luggage on the roof, even if they can, they can't exceed a certain height, so your idea is absolutely impossible. If you are lucky, you will only be questioned and criticized at the checkpoint. If you are unlucky, you will be fined, ranging from 500 to 2000, depending on the inspector's "mood"! And the rest of the journey, you have to face the hotel, or hopeless.
Moreover, the temperature in the plateau area is very low at night, and it is easy to catch a cold when living in a tent.
It snows heavily in the mountain pass during the day, not to mention that camping at night must be looking for a wide area, so strong night wind and extremely low temperature are inevitable, and if you catch a cold carelessly, you will lose more than you gain. After all, in the plateau, a cold is a big or small disease, and altitude sickness should not be underestimated!
Third, it may not be safe at night.
In broad daylight, the security in Tibetan areas is optimistic, but there is no guarantee that it will be so "peaceful" at night. If you really meet a "criminal", it must not be just the price of a room for one night.
So according to the above three points, you really met it, and it only takes a few minutes to spend thousands of dollars. On the contrary, if you plan to book accommodation along the way from the beginning, even if you stay in a low-end hotel or guesthouse, the whole accommodation cost will be about 3000 yuan (Chengdu to Lhasa for settlement). A trip to Tibet, the most basic cost accounting line is 1 000, and it will take at least 1 000 days to get it done. Only when there are many people together can many things be shared equally, so it will save a little. If it is more than 1 000, you can walk for a few more days. For example, it takes 1000 days to get out of Sichuan.