If I understand the methodology correctly this study seems to penalize unlimited plans quite a lot. In the linked methodology pdf they specify that the price for 1 GB of data for unlimited plans is calculated by dividing by the average data usage per user but limited plans are divided by the limit.
For example in Finland almost all plans are unlimited and users regularly use a lot of mobile data. Average monthly use is 34 GB and median 6 GB [0]. The cheapest mobile plan I can find is 9.90€/month for unlimited data at 1 Mbit/s [1]. Dividing it by 6 GB median data use gives $1.95 for 1 GB which is close to the their reported minimum price of $1.75. However if this plan was instead marketed with 100 GB monthly cap they would have divided it by 100 GB instead giving a much cheaper price.
I live in Lithuania and that also appears to be the case here. The cheapest mobile plans from the main operators start at around 8€/mo for 1GB data with unlimited calls and texts. To be fair I would say these type of plans are actually quite expensive compared to the rest of Europe. But there are plenty of data-only plans which work out a lot cheaper.
The cheapest provider sells unlimited data for 2.90€/mo, but the speed is limited and they are a smaller player so their coverage is too. From the big players, truly unlimited data with no speed caps is 20€/mo (the largest capped plan is 120GB for 11€/mo, 0.09c/GB). And of course they have discounts if you have other services from the same provider.
The question is always what fair use is. Phone contracts with unlimited data set the fair use clause in Austria to 1.5TB a month and have no such limitation for data only sim cards (home use).
On the other hand unlimited in Germany often means ISDN speeds after 50GB.
I live in Switzerland and we have quite a lot of unlimited plans without speed limit after a certain amount of data. Also the price in relation to income is not that high. If I compare it to Germany, where you can get no real unlimited plan and very often have a bad signal even in cities, and also in relationship to the income there, Germany seems to earn a place much lower on the list.
So this comparison seems a bit odd, and should be divided into prepaid plans with limited data packages and unlimited plans.
For example in Finland almost all plans are unlimited and users regularly use a lot of mobile data. Average monthly use is 34 GB and median 6 GB [0]. The cheapest mobile plan I can find is 9.90€/month for unlimited data at 1 Mbit/s [1]. Dividing it by 6 GB median data use gives $1.95 for 1 GB which is close to the their reported minimum price of $1.75. However if this plan was instead marketed with 100 GB monthly cap they would have divided it by 100 GB instead giving a much cheaper price.
[0] https://blog.telegeography.com/finns-lead-the-way-in-mobile-... [1] https://elisa.fi/kauppa/puhelinliittymat