There is an old saying :
"Make Hay while the sun shines"
which is really about taking advantage of the situation at a given point in time, however it won't take into account the stupidity of people who won't or are unable to accept that a shortage in terms of supply and demand will occur.
I always add 50% to a 100% to my original quote if someone rejects first and then later realises that they were wrong. (Its usually the HR department anyway)
you should do so too.