100 PEC = 1 PED
1k sweat would be 5 PED at that price.
What they're saying is that they are selling 1k sweat for 0.5 pec each sweat.
When buying items, like weapons, faps and so on, you usually count it as for example tt+10 PED. The value of the item +10 ped is the price. Items who are limited (L) is an exception. Then it's % of the item value instead. Example, a 10 ped limited item with a markup of 110% would cost you 11 PED.