FH4 is only 4 dollars
What country do you live in? For me it’s currently $/€14 in the regular version, 20 for the deluxe ultimate edition.
Also note that the game will be getting delisted in december, so now might be the last chance to get it at a discount.
The only time I tip with counter service is when something is like 3,80€ and I give them 4€ in coins.
At that point, I usually just go “keep it”