What does it mean that MS could hold out so much longer on $100 price cut?

[FilaBrasileiro]

360
299/399 = 25.1% price cut in 3 years
199/299 = 33.4% price cut in 3 years

PS3
499/599 = 16.7 % price cut in 2 years
399/499 = 20.04% price cut in 2 years

If next year Sony cuts another 100 bucks from each sku3

399/599 = 33.39% price cut in 3 years
299/499 = 40.08% price cut in 3 years

If Sony was to cut by the the same % as microsoft then the prices would approximately be:

80GB = 329

160 GB = 449