Autopickup and reload_missiles doubles turn energy cost of the main action (walking/shooting) which is usually cheaper than doing the two actions separately would be.

Some examples of energy costs:
Running on coward with low HP: 800.
Picking up item(s): 1000.
Running on coward with low HP and picking up item(s) with autopickup: 1600 (2*800).
Running on coward with low HP, then picking up item(s) on next turn: 1800 (800 + 1000).

Same behaviour can also be observed with shooting missiles and using reload_missiles to reload new ammo: if shooting costs 505 for example, then shooting + reloading with reload_missiles costs 1010 (2*505) while doing these two actions separately costs 1505 (505 + 1000).

Expected behaviour would be to calculate energy costs for these two actions separately and summing them to give same energy cost as doing the actions separately would cost.

In addition using autopickup or reload_missiles uses only one turn instead of two but this is very likely the intended behaviour.