Resistance dependent pricing for resistors
Some values of resistors and capacitors are manufactured in much greater quantity, and thus cost less. For designs where that exact value of the resistance isn’t relevant (such as designs where the ratio of resistances determines the operation), this is perfectly fine and you can lower costs by selecting these values. If you have a very specific need, and can’t meet it with the more common resistor values, you may have to pay more to get specialized components.