I cannot se how much money you gain or how much money you loose have any impact on the value of a heirloom.
Neither has any sort of effect on the heirloom or the time it took you to make it.
What is important is the value of those 72 hours it takes to make a heirloom. How much cRPG gold is 72 hours of your life worth...
It takes time to earn gold. That's why it's relevant.
Hence the calculations: Generally you would not to spend more
time earning the gold to buy a heirloom than the
time it would take for you to heirloom it yourself.
You might spend a bit more if you have tons of gold in reserve - but I don't know what portion of the population has millions in reserve. For the rest of us, these calculations help us decide: Should I save up enough money to buy the heirloomed item I want? Or will it be quicker for me to just level and retire enough that I can heirloom it myself?