This is a good perspective. I pushed for a higher priced pen test firm in our last engagement due their name/reputation (i was sick of nessus scan outputs) but ultimately their price was just SO MUCH cheaper than the prestigious named one. I couldn't provide a justification to leadership outside of "they have these awesome writeups in their research division". Asking to see a sample report to prospective firm turns out to be a crapshoot as well (but seems to be one of the few things to go off of). Can you provide any insight on how you evaluate?