This forum is for LoRaWAN on TTN/TTI that is funded by TTI so we don’t do LoRa point 2 point.
I have no idea what you paid for it, I can only see what it sells for, so a poor comparison, but you should look harder. I’ve sourced new gateways for £20 and there are plenty of old Helium gateways going cheap that can be repurposed.
And if the Milesight is so expensive, why not spend a little more to do the job properly?
Additionally, you only get to turn it on & off 5 times a day on TTN due to the Fair Use Policy. So it may be better to sell it and use a different system.
Or get another Milesight device and reverse engineer their D2D protocol to implement on the Duinotech.