What does "spending hours" mean? Is it used as sarcastically?

Native speaker’s answer
Rebecca
"Spending hours" is not used sarcastically here. "Spending hours" means "dedicating hours" or "taking hours". He is saying that the workers at McDonald's use hours of their time at work to make Egg McMuffins. You can use "spending" for any unit of time, such as seconds, minutes, hours, days, weeks, etc. Ex: I've spent five days writing this paper for my literature class. Ex: She spends twenty minutes every morning doing yoga.