RE: Is SBD a good investment now?
The peg target is how much you get when converting 1 SBD. Normally you get about $1 worth of STEEM (delivered 3.5 days later as you noted in the post). However, you currently you get about 85c worth of STEEM. That's because, if every SBD is viewed as worth 85c, that brings us to the enforced 10% cap.
Is there such a parameter inside the blockchain?
It is in the blockchain code and also discussed in the white paper.
Furthermore, if this is the case, do you have roughly a formula for calculating the ideal/desirable SBD price?
MIN(1,STEEM supply * STEEM price / 9 / SBD supply)
Be cautious about coinmarketcap, especially their overall price. They can sometimes include some nonsense prices from questionable exchanges, including as their assumed Bitcoin price which affects all the other prices (since STEEM and SBD trade against BTC). Look to only prices from reliable exchanges. That's mostly bittrex and binance (for SBD and STEEM) and coinbase/gdax, gemini, bitstamp (for BTC).
Last, can you provide me a link that explains the past SBD overpegging the best?
I'm not sure but if you want to look for some posts and discussion on the topic I would suggest blogs from @timcliff and @buggedout
Damn, they promise $1 for 1 SBD and now something like that.
No, it doesn't "promise $1". It promises $1 only when the STEEM price/market cap is high enough. This is written up in the white paper.
okay... wow, seems I need to go back and check the WP.
thanks! it's nice to start my day (in taipei) with something I didn't know. :)