Depending on what version of the mini chassis you are looking at, they include the bottom metal which can offset the price some. I usually get the EH1 Elite Hunter (Gen 2 mini chassis, Proof Sendero profile, SA) from Altus and its sets me back about $1k and is ready to go as is. Plus I don't have to wait for them to be made. They are light weight and pretty much everything I need and nothing I don't.
If you are looking for affordability and performance and want to use BDL type floorplates, the GRS Bifrost and Warg are funky but extremely comfortable and functional. They are often overlooked and sort of like high end polymer stock with the features of a chassis while maintaining more stock like weight. The barrel channels are pretty forgiving if I recall as well.
I liked mine, the Bergara B14 is garbage though, otherwise I would have kept it.