A parking meter, a slot machine, that coffee machine at the office - a "Groschengrab" is anything that takes a disproportionate amount of your money. "Groschen" were worth 10 "Pfennige," or pennies, before the euro was introduced in Germany. If the money "Grab" ("grave") stopped at a few "Groschen," that wouldn't be so bad. But by nature they tend to be insatiable.