$5 method: 2x4s modified with steel at the end to hook to the back gate and function as a simple ramp. I've used this to load all sorts of big stuff.
$15 method: For taller trucks and heavier loads, you can add to the capabilities of a ramp with a $15 winch puller (aka come-along). Dowel rods underneath the object will make this even easier.
$150 method: A Harbor Freight hydraulic lift table, when they go on sale. This is also good for moving the stuff you've lifted up, since it rolls. The downside is getting stuff up onto the table. Even compressed, it's about 11" tall.
Other $150 method: A Harbor Freight shop crane. A little scarier when something's swinging in the air, but you don't have to get anything underneath the load.
The only situation where an overhead hoist or a motorcycle lift would make sense is if you're always loading in the exact same spot. With the lift, you'd have to find a place to put it where you could still drive over it. I use my scissors lift for this. But it's not always convenient to bring the heavy thing into your garage first.
You can throw a hydraulic table in the back of your truck.
Ramps can also fit in the truck. And there's no beating the price. If you bridge the 2x4s to make a fixed width ramp, you can get the load on it, and then jack the low end of the ramp into the air so you're just sliding the load over into the truck bed. The jack will do the hard part.
I'm lazy and I'm poor.
