why is this LM338KSTEEL so expensive

its $54 
regular LM388T is only $2

http://www.mouser.com/ProductDetail/Texas-Instruments/LM338KSTEEL-NOPB/?qs=sGAEpiMZZMvu8NZDyZ4K0bykmGFCCERa

whats the trick ?
i read the datasheet, only difference is; it can handle  higher/lower temperature... 

rare part (metal to-3 package)... low volume = high prices.

JR

  I have a few of those, but I didn't pay even close to that, more like $5 I guess. I don't know why they are like this, is not TO3 is a rare process, but probably quite obsolete.

  There is other difference, thermal resistance, junction to case. The TO220 has 0.7ºC/W and the TO3 1ºC/W. Put this way the TO220 is better, but the TO3 might get a lower thermal resistance case to sink, so maybe there's a compromise. In any case, it doesn't make sense to get the TO3 part unless replacing something where you absolutely can't fix it otherwise...

JS