Like RStrahan has indicated, you may not have considered a very important portion of the cost approach, goodwill.
Also, you have to understand that these McBurgerland franchises are a unique animal when it comes to buying land. They rarely consider market value when they buy land. I have worked on a few McBurgerland appraisals, and have a close friend who owns 4. When corporate designates a need in a new location, they find a location which will produce the highest revenue. Period. Circumferential access, road exposure, adjacent mall traffic, proximity to major roads, etc. Then they back in to the price they are willing to pay, by estimating revenue, backing out hard costs, which reveals what they are willing to pay for the land. Then they go and buy it, with little concern of what the true market value is. My dad sold a parcel to a Wendy's in Cape Canaveral, FL about 8 years ago. They came to him, and offered him a very high price, oblivious to the fact that is had been offered for sale (but not in MLS) for 33% less! Everyone was very happy.
McBurgerland came in within 6 months and paid TWICE what my dad got, for a similar parcel a block away. Ends up that the Mcburgerland is the highest grossing location in the county, and the Wendy's is #2, so these guys are not dumb, they just go about acquiring land a little differently than most...
The point is, you need some specialized experience if you plan to do a good job on a big name fast food property, because the buyers typically do not buy based on value, but on their estimate of potential revenue and this does effect the true market value.