Your neighbor is being transferred, so he/she has a real motivation on moving. Your neighbor could have a back-end transfer package where his company will pick up all the expenses and reimburse the homeowner their equity. If that is the case, he just wants to go.
I am very familiar with the area you are talking about and it has gone through some obstacles: One, being or going to be annexed into the city which equates into higher property taxes. Second, lot prices dropped between more expensive neighborhoods and builders kept on building - making it much harder to sell pre existing homes versus brand new ones. Third, growth of the surrounding area with road congestion and commercial businesses. Then last, the national media effecting our local market causing a huge buyer's market (our economy is stable, we have low cost of living, low unemployment and the interest rates are extremely attractive) still buyer's are waiting to see what will happen instead of taking advantage of a golden opportunity.
Your neighbor may hurt the comparables, but realize this is only one sale and it was a less expensive home - I am assuming your's has more upgrades than theirs.
I would be happy to do a market update and see exactly what the totally picture of your neighborhood is really doing.