I had a desktop PC that I bought (as a pile of bits!) with 512MB of RAM in 1999 and I sure as hell didn't pay more than a couple of hundred for memory. That might have been EDO rather than SDRAM though but I can't see the price difference being that much!
https://news.ycombinator.com/item?id=47551166
>128MB DIMM: May 1997 $300. July 1998 $150. July 1999 $99. September 1999 Jiji earthquake happens. September-December 1999 $300. May 2000 $89.
>Then overproduction combined with dot-com boom liquidations started flooding the market and Feb 2001 $59, by Aug 2001 _256MB_ module was $49. Feb 2002 256MB $34. Finally April 2003 hit the absolute bottom with $39 _512MB_ DIMMs
In 1999 512MB could cost $400, but it could also cost $1200 :)
My computer had 16Mb in 1997, and it was lower-range but not the absolute bottom.
It looks like Anandtech listed 128Mb for $300 (not inflation adjusted) in 1997. It fell to $150 in 1998 and by 1999 you could buy it for $100.
So 512Mb RAM by the end of 1999 for ~$200 was plausible.