What we learned about the OnePlus phone based on the Snapdragon 855 and the Snapdragon X50 5G NR modem is that the phone will cost more than the OnePlus 6T. This is not a big surprise as every generation of OnePlus phone ended up slightly more expensive than the previous one.
OnePlus 6T just launched and it is starting from €/$ 549 or £499 and it ends up at €/$ 629 for the 8G with 256GB of storage.
The 2019 5G phone will start at $/€ 649 at least according to the people close to the matter. It is likely that the successor to OnePlus 6T, let's call it OnePlus 7, will end up being a 4G phone but there will be a 5G variant too.
The current trend in the phone industry is that every generation the high-end phones end up higher, and consumers still are willing to pay for it. Obviously, the market is pedaling in the wrong direction but hey, if it makes you happy to spend $1449 + Tax or €1649 for a flagship iPhone who are we to stand in the way of your aspiration to happiness? Money can buy shiny objects.