Tons of money!!! HA! YA cant take it with you!
Enjoy
When I buy parts to build these things it amazes me how expensive it is to buy them in the small quantities that I deal with,
Some ic's are $10+ easily, parts like resistors are pretty cheap, electrolytic caps are costly as well, add the power transformer $$$$, a case $$$$$, panel engraving $$$$$$$$$$$$$$ an amp like the inverting O2 when done is easily $150 - $200.....
But you can't go out and just buy one readily....especially if its a one off design. Which makes them very desirable to a guy like me!!! LOL!
Alex