They're trying to get more than they're paying for.
It's a literal expression, and is a variation on "you get what you pay for". Its connotation is slightly negative, and it just means that they're trying to underpay.
Here are some examples:
You’ve found your dream job on one of the job boards, or maybe even on the career site of what you think could be your dream company. Uh-oh. The title of the job doesn’t seem to match the responsibilities and expectations. Are they trying to get more than they can pay for? Or, the job description is far too brief.
Toxic Interview Culture
Freelancing is hard. We spend half our days selling ourselves and our ideas, the other half chasing clients for payment — then sleepless nights worrying about when we’re going to get the actual work done. Clients are forever trying to get more than they paid for.
Attention, freeloaders: That coffee shop is not your office
I was accused by the thick, darker skinned african-american gentleman of trying to get more than I paid for, saying OH, you only ordered a Medium but you want the rest when you didn't get a Large??
When another employee went to remake it (which had way too much of the syrupy/sugary strawberries they used), I explained I ordered and paid for a Large, and not the Medium I was given, and the accusatory gentleman just stepped away with no manners to correct himself, just a smirk on his face, didn't even acknowledge that he accused a customer who paid for a Large of trying to get more than was paid for.
Yelp: Smoothie King