Just going by the ones I built, there was roughly £400-500 in parts. They took me a weekend so I charged about £150.00 to build them.
Hence I sold the A30 for £500 and the A60 monoblocks for £1100.
I could happily knock a bunch more out but seeing as it’s a non commercial design etc I never felt all that happy asking £500+ to knock an amp together.
Parts prices could have gone up substantially of course.
Two 8-hour days and you’re on roughly the minimum wage. Of course if you kick off at 09:30, quit at 16:30 and take a couple of hours out each day for breaks then the rate’s a good deal better. But still not remotely
near what your local garage will charge for a mechanic. The silver lining is you might actually enjoy it .