Follow Anders question

Anders, here we have a problem because you are supposed to reach Hainan without going through mainland China and that is valid in both cases, for Hainan 30 day visa free access and for Hainan VOA. I understand that the flights through China area more affordable, but they are simply not eligible for any of the two mentioned options, unfortunately. In other words, you need a prearranged Chinese tourist (L) visa to perform such a journey. Of course, in this case, if you obtain a prearranged tourist visa, you don't have to bother with the above mentioned visa free or visa on arrival options because a Chinese visa covers entire mainland China including Hainan.

Now, when you know this detail, you should think about the entire itinerary because the option with a prearranged visa allows you a travel that is more flexible. One more detail... You can use a travel thorough China to reach Hainan, but only if the airport immediately before Hainan is outside of China. In other words, you can create an itinerary:

Oslo - Beijing - Hong Kong - Hainan

As you can see, this is allowed and you can travel through China using 24 hour visa free transit. When you have reached in Hong Kong, your travel through China is reset and you are free to travel to Hainan using 30 day visa free access.

My suggestion is, play a bit more intensive with different flight options and see whether you can create an itinerary that will be more affordable than the option with obtaining a Chinese visa in your home country. If you have some other ideas, doubts or questions, here we are hoping that we can really help :)