dathin I suspect that lokki 's suggestion to use an arduino will be a bit more expensive.
It's probably comparable price if you use a PJRC Teensy LC instead of Arduino "proper". Here' s the USD price difference:
https://www.adafruit.com/product/781 ($12.95)
https://www.pjrc.com/store/teensylc.html ($11.65)
Considering shipping and where you get if from the price delivered to your door is probably fairly close, so cost would not be a decision maker between the two options.
The reason I ended up going with the USB backpack is the PCB layout is organized to plug the LCD right in, pin-for-pin so assembly is really simple to wire it up.
The place the Teensy LC makes sense is if you want to do more with the microcontroller than simply emulate a MatrixOrbital style display via USB. For example, you have up to 13 pins you can scan with the ADC, which means you could have 13 low-speed ADC channels (for example, potentiometers or other type of sensor), all stuff you can poll from Bela and you have the microprocessor on the Teensy to do a lot of low-level processing to take it out of the Bela CPU cycle time.
The USB backpack uses a Teensy 2.0, which uses a much less capable processor. My firmware modifications (forked from CanyonCasa) pretty much use 100% of this device, but the same functionality would be a drop in the bucket for the Teensy LC.