€4.50/GB is absolutely insane for Europe. In Italy you can get 50GB for €7 From Kena or ho.mobile (€0.14/GB) or 50GB for €8 from Illiad (€0.16/GB). All at 4G speeds.
https://www.kenamobile.it/prodotto/kena-6-99-limited-edition...
https://www.kenamobile.it/prodotto/kena-6-99-limited-edition...
Despite this, I can see this service being popular among companies who are willing to pay a bit more per GB to avoid negotiating with operators and getting SIM cards all over the world.