Monoprice: MP Select PLA Plus+ Premium 3D Filament, Black - 4kg for $38

Monoprice is offering their black PLA+ 1kg filament spools on sale for $12.35. By adding 4 spools to the cart and $0.60 worth of filler, and using promo code 'NY25', the price further reduces by an additional 25% off, making it $9.44 per kg with free shipping. You can find clearance items for less than a dollar for filler on their website.