We used them once to clean out the garage at the rental property. It cost under three hundred dollars, but they pretty well filled a short stake truck. Some of the stuff was pure landfill; some was easily recyclable but bulky; some was considered hazardous (lead batteries, etc.) and would cost them $ to dispose of (they pass that cost along so that's why sometimes the price quote is nebulous).

In the space of 2-3 hours, the stuff was gone. If we'd tried to get rid of it ourselves, we would have had to rent a truck (unlikely the size of a commercial stake truck), move everything, and pay to dispose of it. So, from our perspective, it was well worth it. $50 is a steal, but, as was suggested, make sure you know exactly what will be charged for. It sounds like a come-on price though it may be an off-season time for them and they just want to keep people busy at some price.