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.
Apparently, signature that I used from 2006 no longer tolerated so now deleted.
getting your hammock ready for winter hanging can get expensive real quick