Price volatility is known and people have to accept price slip during their trade processing time. However it should not be a barrier against trades with bitcoin as a payment method. Probability that price suddenly falls 5%, 10% or 20% during your trade processing time is very small.
A bigger barrier is expensive on chain transaction fee, not price volatility.
I think even dropping 1% is near impossible during a trade itself, I mean trading is something instant, so it should be a very tiny thing if you are not taking your time, if you keep waiting for a better time to trade then maybe it will happen, but normally only a few hundred dollars could move at most, probably not even as high as hundred dollars when I try to trade because I do it very quickly.
In the end, people should realize that it's easier to just focus on doing better, and because of that it's easier to handle all of this, because we know what we are doing and it shouldn't be something we worry about at all. Bitcoin will continue to be great and transactions/trading will get faster and cheaper in the future when we solve those issues.