The answer to your question could be all of the above. However, the other problem could be that the Bank may not actually know what the local / legitimate comps are for that property. I've run into it numerous times where Banks thought a property was worth much more based on old comps, comps that weren't really legitimate comps or did not actually know the condition of the property. i.e. the Bank thinks it is a move-in ready unit that is wonderful; in reality the copper pipes and furnace have been stripped out and there is no functioning condo association. Another issue is that the Bank may have decided that 79K is their minimum to make their numbers work.
I would suggest you provide them with your list of comps that shows what similar units are going for and see what happens.
"The Code is not a ceiling to reach, but a floor to work up from"
