Terratrike and Wizwheels make some of the lower-priced tadpole trikes (recumbent trikes with two wheels in the front).
Sun makes the lowest-priced recumbent
delta trikes in the US, at $800-$900 or so for the lower-end ones. Sun has phased in some newer bike and trike models this year, so the older ones may get blown out at lower prices; if you are willing to pay new prices, it is worth checking into at least. The Sun old-style delta trikes seem to have frequent problems with the rear-axle cartridge bearings being ****. A few people I have heard of (online) have spent their own money to put in better bearings than what Sun uses.
The next delta trikes I know of above the Sun cost at least 2X more.
KMX makes some cheaper models. These don't have full-range gearing but with an engine doing most of the work that may not matter much-
-out of stock until September.
KMX trikes are built heavier and don't seem to perform as well as other recumbent trikes, in pedaling
use. KMX tends to stress the ruggedness
of what they sell.
There are a few companies that make upright delta trikes (granny-style trikes) but the recumbents are generally way, way
more comfortable to ride.