I’ve given clues about importance of price sensitivity, its relative.
Assume average price charged for hot wax as up-sell is $4.00 and sold ratio is around 20 percent.
$4.00 X 0.2 = $0.80
If average revenue for express exterior is $9.00 before hot wax, it would increase to $9.80 after adding it.
In my area, express exterior is $4 to $12 and full-serve is $14 to $20. In-bays are $5 to $10. Most conveyors charge $4.00 for hot wax.
I have a friend in Mass. who charges $30 for full-serve and top express exterior wash is $24. His in-bay starts at $10 and tops at $18. He gets $6.00 for hot wax.
This is why it’s unwise to use information provided in product advertisements to analyze a market.
Best practice is to analyze the trade area to determine appropriate pricing strategy.