Only the verbal noun κυρίευσις (this way of constructing derivational morphology was not applied to this verb ending in -ευ in Ancient times but later it was) (and it is now written as κυρίευση in Standard Modern Greek) exists in Modern Greek along with the continuing verb κυριεύω.
Consequently, to compare Buth's reconstructed pronunciation with the Modern Greek pronunciation, you would have to look at a word with a similar ending in a standard Modern Greek Dictionary. One such word ἁλιεία (Triantafyllides)
It is the activity that an ἁλιεύς does (for a living / as a profession) when he and his colleagues go to ἁλιεύειν. (See ἁλιεία (LSJ)
for a similar linguistic contraction to what we were discussing in the other thread)
[As for the obvious question arising
from this as to why ἁλιεία survives into Modern Greek, while κυριεία does not, I think it has to do with the range of meanings covered by the other words in the meaning-group. ἀγκιστρεύω "fish with a line and hook" is still in Modern Greek as ἀγκιστρεύω and that hasn't changed its position in the scheme of "fishing", ἁλιεύειν is still there as ἁλιεύω (without so many diacritics though). What Modern Greek does have is another newly formed word ψαρεύω which derives from ὀψάριον "fish" (which you intend to eat or are eating [a nuance, which I think is significant in John 21:10 which you can look at by yourself if you are interested], as opposed to ἰχθύς which has a much broader sense of meanings) with which we are familiar in the New Testament. Modern Greek ψαρεύω also means fish, as in standing with a net in the water or trawling from a boat rather than angling, but my impression is that it is more down to earth. There is also a corresponding noun ψάρεμα "fishing".
The word ἁλιεία that I suggested you look at is now used more in the big sense "fishery" (big picture) rather than "fishing" (hands on the job) a meaning covered by αλίευση (another post-Koine creation along the lines of κυρίευσις described above).
That is to say that the word ἁλιεία - a borrowing from Ancient Greek (Greek has an ongoing borrowing tendency throughout the Byzantine period, not just from the point of the revival of venacular literature as in some other European nations) - has a more formal / scholarly role in the Modern Greek language in a similar
way that Latin derived words do in English.]