No one cares how much effort went into it. They only care about the results.
The mediocre, knock-off quality of the submissions is such that they shouldn’t be paid even if they spent an eternity on their crap.
Also, in the case of software: it either works or it doesn’t, so defining the job in its specification is reasonably clear. But what does it mean for a logo to work? How does one sort out the influence of the logo on sales of a product? If you could do that at all it would be long after the job had been done and paid for.
Lastly you describe the situation of someone coming to your house to do remodelling work. But that is like software development: you clearly specify what is to be done and have measures of the quality.
To be fair, this is part of why I advocate splitting the creation of the concept from the physical production of the logo. If the graphic “artist” is expected only to act as a technician who can make efficient use of the tools to produce the verbally specified deign then that one person can be selected on the basis of his existing portfolio and be guaranteed payment of an amount likely to be satisfactory to all concerned.