Even a so-called "key date" 1997 S5Y Color Silver Panda PF69 was sold for US$199. What kind of "key date" gets sold for US$199? 
Uhm, the kind I like to buy in large quantities?
But in actuality one of those sales you refer to was a 1997 S5Y Colored Panda 'PF 69' for US$199 (not an Ultra Cameo). The current ask on a 1997 S5Y Colored Panda 'PF 69 Cameo' is US$199 with no Ultra Cameo available for sale. In fact there is only one graded 1997 S5Y Colored Panda for sale on ebay right now.
Only two 1997 S5Y Colored Panda PF 69 UC have sold since January. Only two graded 2001 Panda Small Date, a 69 and 70, (a Key Date) have sold since January. But the 2001 Small Date 69 is several times the price of the 1997 S5Y Colored Panda PF 69 UC.