I paid $10,000 for a new roof in 2005, 30-year shingles with a warranty. Mine was a complete tear-off of three layers and it needed new plywood because the original roof was wood shingles nailed to boards with spaces between. Are you sure your neighbor is even removing the old shingles on his? Usually with one layer, the cheap contractors will go right over it with the new, which is allowed by code. At any rate... if you've got a complete tear off, the labor for that is half the cost of the job.