For those of you who use a Hong Kong PSN account (not very difficult to set up and get hold of HK PSN cards), there is currently a 50% sale on selected fighting games.
Included are the psOne Classics: KOF97, KOF98, KOF99, and Samurai Shodown III. Each now costing HK$16 (Just a little over £1!!)
Whilst the conversions on ps1 are not that great, KOF98 (which i already own) loads between rounds and if i remember correctly music also restarts each round, the prices are actually very cheap.
More details can be found here.