I bought my bent bike new in 2011 for $700. I added about $400 worth of accessories to make it a good commuter, but that's not an unreasonable price for a good but not super high end DF bike.
Sure there are a lot of higher end, more expensive bikes and trikes, but if price is your main driver, you might just have to look at some of the off brands that aren't necessarily made or marketed in the US.
I think TW-bents may still have a few vendors in the US. The guy I bought mine from used to be 'Action Bents' in WA.