Sorry man but I have to say this...
Being able to overclock something past its design hashrate is great, but that extra hashrate comes at a cost. Having the fans run constantly and the hardware running harder adds some risk to the investment. You're expecting that extra hashrate to equal an increase in value, which is absolutely true, but the extra value shouldn't be proportionate to the original $/Gh basis that you're calculating the value on. If your buyer is making extra BTC by running it harder, that harder risk should be rewarded. Maybe increasing the value by 50% on extra hashrate rather than 100% would make more sense, at least to me anyway.
Another example of this would be the eruptor blades. They shouldn't be based on a 13gh/s value, but rather a 10gh/s with an overclocking incentive.
This is just my opinion, if you don't agree with me then just ignore my post.
Blades are probably the worst example to use. They are NOT overclocked at 13GH, they have two clock settings - allowing the user to choose to prioritise power consumption or hash rate.
Avalon based OCing is 'true' overclocking, but at the same time there was headroom built into the chips. Yifu said recently "you finally found it", as he'd posted within the github about this some time ago. There is some risk like everything in bitcoin, and nothing else. You can choose to run the unit at 85 (or higher, I don't have the right cooling here and have to sleep next to this unit) or at 66.
Every bid so far has been for a 66GH miner, I don't think anyone is attaching directed worth to the overclocking as no one can gaurantee it. And think, if I was truly increasing the price proportionally, @100GH that'd be 150% market price for the 66GH units - which I'm no where near.