The main difference between an ICO and IEO in terms of marketing is that the former requires heavy marketing like roadshows, google , facebook ads etc but the later doesn't require heavy marketing to reach softcap.

Do not make a deal unless you make sure that all the payments "maximum values" have been deposited to the collateral so you can start making the deal.
With regard to price fluctuation, you can request that the transaction in stable coins and then pay the conversion fee to BTC.
The collateral can bear any excess costs to the second party and stable currencies will improve stability.

I may consider greediness as a tool to encourage people but somehow it is also a reason for our fall. This simply means that we know also to be satisfied with a small amount and accept what only got. Greediness could sometimes lead to illegalities and yes, it often to happen in some local businesses. We've been run through this kind of behavior but we should have to control it.