Did you do any winter camping before you took up hammocks? Where you sleep is only part of the picture.
You can double things up. It's "layering" - just like clothing. Use two top quilts. Put a second hammock under the one you sleep in, with plenty of insulation between. Use an extra poncho or tarp to block the wind from the side or below. Car camp - you can't carry (or pull) all this stuff until you have a good system worked out. Test in your back yard at first.
I have spent a toasty night with two 20+ year old summer weight pads under me at ~18F, probably as warm as I have been in a hammock. But comfort is an issue for many, as is sweat/condensation. A few are fine with pads in hammocks, but many hate them. I think you will be way better off with a double layer ( pad pocket ) hammock, just makes it easier to deal with the pad, keeping it in place. Though I think Fiddleback does fine with a single layer hammock and a wide pad. The pad will need to be wider than on the ground.
I think a pad in the pad pocket of a JRB Bridge hammock reduces comfort very little if any ( but also depends on the pad), but in other hammocks I find pads a bit more of a challenge.
But cheapest? No contest, pads. CCF pads will do fine, because all you need is insulation. You don't need cushioning like when you are on hard ground.
For I consider that the sufferings of this present time are not worthy to be compared with the glory that is to be revealed to us....that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God. For we know that the whole creation groans and suffers the pains of childbirth together until now.
getting your hammock ready for winter hanging can get expensive real quick