There's no discount for helping your Luggers, but you're always welcome to pitch in — especially with smaller items or clearing a path.
On a standard Lugg, you're charged based on actual labor time. If you're tight on time, an extra set of hands can help speed things up. The faster everything gets loaded and unloaded, the less labor time on your final bill.
On partner store deliveries, the price is a flat rate set at booking, so helping won't affect the cost.
Want to keep costs down? The biggest time-savers are having everything packed and ready to go, keeping walkways clear, and reserving elevator access if you're in an apartment building.