I bought a 30F down quilt for a bike tour and believe it's the best gear purchase I've ever made. I splurged a bit and bought a nice one made by enLightened Equipment, a bit over $200 ten years ago. (I've finally learned that sleeping insulation is not the place you want to cut corners.) In addition to lower cost, bulk and weight, one of the advantages I discovered is that it stays clean. A few minutes of sun every few days disinfects it easily. I've never had to launder mine.

I'm sure the one I bought costs quite a bit more than $200 now, so I didn't recommend it to the OP. To go cheaper, you'll probably have to get a heavier, bulkier synthetic. There may still be kits and homemade versions on various backpacking forums. It looks like the synthetic "Ray-Way" quilt kit is still available: https://www.rayjardine.com/ray-way/Quilt-Kit/index.php