k31's are known for their accuracy. Can really get some good results if you handload.
As far as Mausers, all the Yugo M48's I've had shot MOA. The M24/47's are said to be even better shooters. Again, handloading and possibly a new trigger will really help.
I have a German k98 that has outshot any milsurp I've had.
I'd lean towards a Yugo, but the k31 may be your best shooter for the $$ except ammo is expensive unless you reload.
Prices: Online and around here, the m38, m44, and m91/30 are all priced about the same--atleast within $25-50. The fact that youor m38 is from 1944 makes it a little rarer I believe. Mosins typically aren't an investment per se, but are meant to be enjoyed