Frankly you may be late in the game. I've bought many K31s in the last couple years, to include several of the JG $200 offerings, I think 6 of them. My prior K31s were nicer. We are at the end of them I fear. My recent 6 were all equal in quality; handpicked. Wood is solid and okay. Metal is worn in many spots on barrel and other spots. Bolt and receiver look practically new. Bolt could have been machined yesterday. At $200 a steal. At $300, unless you REALLY want a bayonet... eh. Maybe if you just really have to have one for your collection. Otherwise, ammo is now getting scarce again and unless you did like I did (buy up quite a lot) then you'll have a $300 surplus rifle with no ammo.
My K31s from '06 were much nicer and seems to me around $150.
The ship may have sailed on the cheap K31s and ammo. Consider a Mosin while they are still sub-$100 and buy a crate or 5 of ammo.