I wish they will bring a €200 device with GrapheneOS out
So, 7a at your pricepoint:
https://www.ebay.com/itm/820099695470
But, it's only supported for 1.6 more years.
So that puts it at $143 per year of support. While the 10a [1] will be supported for 6.4 more years, which puts it at $55 per year of support.
I'm curious how many months/years before out-of-date GrapheneOS becomes the worse option security wise compared to various brands' stock Androids. Obviously it is nuanced and there's no clean answer but it would be interesting on average.
We could think of metrics in public patches, but GrapheneOS has exploit protections that prevent against 0-days which would be hard to factor in.