The 10k pizza guy could have gone crazy if he kept thinking about it - so you should mentally freeze the current value of any spent coins at the time of purchase. But they won't believe you anyway, so let them figure it out the hard way 
The 10K pizza guy is mentioned a lot. There are 2 ways he could choose to look at it:
The first way is to see that purchase as the first BTC transaction to enable and get the market going. By making that purchase he started a process that made his other previously worthless coins skyrocket in value.
The second way is to forever fret about how many millions he lost out on.
Hopefully he looks at it the first way. BTW I assume whoever he is still probably has several 10K other coins and has done very well regardless. Remember that pizza transaction happened in the very very early days.