Most of the gas/c-stores that are not doing well charging $10 for a wash are those which are still using low volume, touch-less in-bays. This usually means long waiting times, a grim looking wash-bay and barely acceptable wash/dry quality. After spending $70 for a fill-up, that is why people don't want to use them.
Several weeks ago, I visited a gas/c-store that pumps about 400,000 gallons a month. The carwash (express conveyor) did over 400 high quality washes on a Thursday. The top package at this place was $12.00.