Творческий доход. Оцените правильность написания кода, пожалуйста.

Курсы Условия
1

var buy = 4000;
var discountedBuy;
if (buy >= 1000 && buy < 3000) {
discountedBuy = buy - (buy / 100 * 5);
} else if (buy >= 3000 && buy < 5000) {
discountedBuy = buy - (buy / 100 * 10);
} else if (buy >= 5000) {
discountedBuy = buy - (buy / 100 * 15);
} else {
discountedBuy = buy;
}

2

Неплохо, но можно покороче и попроще:
var buy = 4000;
var discountedBuy;
discountedBuy = buy;
if (buy >=1000 && buy < 3000) {
discountedBuy = buy * 0.95;
}
if (buy >=3000 && buy < 5000) {
discountedBuy = buy * 0.9;
}
if (buy >=5000) {
discountedBuy = buy * 0.85;
}