Thanks for the answer, do you know the average cost of development of a custom firmware in general? I know it's kind of a large question,may be you you have same example ?
I think it doesn't cost anything to develop a custom firmware unless if you are hiring a developer to make a miner custom firmware.
Usually, some developer here on the forum takes a 2%-5% dev fee they just take a small hashrate from your miner.
Sample Braiins OS takes 2.5% dev fee or ASic.to firmware they take 2.8% dev fee.
If you are looking for those custom firmware you can check this section "
Mining Software"