I picked up a nice one at a gun show with the mum & monopod in exc condition for $300. Arisakas are common at gunshows. The highest price ones I have seen are around $400 have mums and are in VGC.
Rule of thumb seems to be if the mum intact, it will bring + $50 to $100 depending on overall condition.
There are many 99s with ground mums & great bores around if you want a shooter.
There are many 99s & 38s on the auction sites, however IMHO most are way overpriced.
The takedowns and the T44s are rare & will cost more.