What cheap general purpose MOSFET to use?

The 2N7002 or 2N7002K MOSFET is one of the best MOSFETs to use if you just want to have a general purpose switching FET.

It or its variants is available from many manufacturers and at all distributors.

On LCSC, for example, one reel of 2N7002 from chinese manufacturer HL, only costs 15.90€, that is 0,0053€/pc