For modern lenses, from the big four manufacturers, what have you been buying and selling them for on ePay, over the past 12 months?

Is there a cycle to the prices of lenses? Are summer prices higher, and holiday/winter prices lower?

My results over the past year, for mostly newer and clean, near mint lenses:

75/6.8 Grandagon-N, early 90s, bought for $465; sold for same

90/6.8 Grandagon Sinaron-S, green stripe, bought for $475, sold for $520

90/4.5 Grandagon, green stripe, bought for $900

150 Sironar-N Linhof, white strip, bought for $325, sold for $400

180 Sironar Sinaron S, white strip, bought for $375

250 Tele Arton (older, it's a 12 million serial number in a Compur Press - probably 1970s) bought $305
(saw a newer Tele Arton in black copal go for only $430 last week... darn)

300 Sironar Sinaron S, MC (early 1980s), chrome dial Copal 3, coating marks, bought for $400, sold for only $305 (ouch...)

It's kind of like the stock market. I've slightly ahead, but have had some nasty crashes...