They're quite cheap and "trivial," honestly - iNav, ArduPilot, and PX4 are all strong in this space, and controllers start in the $50-$60 range (look at Matek hardware). Of course, for some definition of "trivial," but we do live in an age where a fairly accurate MEMS gyro/accelerometer, a barometer, and a fast STM32 microcontroller can all be had at a low price, and the control algorithms are mostly tried-and-true PID / feedforward PID attached to some form of input filtering.
One can definitely build a fully autonomous flying wing for under $200, especially if the foam is self-cut. There are also a wealth of cheap foam pre-molded models available these days. We're really in a golden age for DIY flying models right now, pending regulatory crackdowns in most countries.
Yes, pitot tubes have been supported for a long time by all of the "mainstream" flight control software (PX4, Ardupilot, iNav although in iNav it doesn't do much besides provide an on screen display readout). Both analog and digital (I2C) pressure transducers are generally supported by direct interface to either an ADC pin or the I2C bus, which is exposed on most boards, even those designed for quadcopters.
Many Ardupilot and PX4 boards are starting to come with CAN ports as well for UAVCAN peripherals.
One can definitely build a fully autonomous flying wing for under $200, especially if the foam is self-cut. There are also a wealth of cheap foam pre-molded models available these days. We're really in a golden age for DIY flying models right now, pending regulatory crackdowns in most countries.