I layer mine in a folded wool army blanket, roll the whole thing together and slip into 2 of those bags that folding camp chairs come in and put the roll behind my 2 front seats. It also fits on the rear fenders as long as the soft top is up in safari mode.
For the first 2 years anyway, now I leave the blanket out normally.
As for cost: almost 18 years of my life so far for the blanket and about 10 bucks for the bags, but it came with 2 free chairs... you could do it cheaper and not join the army and use one of your wifes sheets instead. Wait, maybe that's more expensive, I don't know...
'05 TJ SE, 2.4L, NSG-370, NP-231, D30/35, Procomp 2(+)", KM2 33x12.5", TAG Flat fender flares, ZJ steering, JKS Quicker Disconnects, Airraid, Cobra 75WXST, super-comfy racing seats. On the garage floor: axles, JKS 1.25 BB, BMML, Rockkrawler T-case skid, .75" spring spacers...