Sometimes you don't know how many times to repeat: it depends on the person using the program. A common pattern is to keep going until they type a special value, called a sentinel:

total = 0
price = float(input("Price (0 to finish): "))
while price != 0:
    total = total + price
    price = float(input("Price (0 to finish): "))
print(f"Total: {total:.2f}")

Notice the program asks twice: once before the loop, to get the first answer, and again at the very end of the loop body, to get the next one ready for the condition. That shape, ask, then loop while the answer isn't the sentinel, is worth memorising.