Well done nonetheless, seems to work pretty smooth (though I see a lot of mixed materials in the buckets?).
I tried to buy a bunch of 44 specific lego pieces (the parts were listed from a book and fairly common) through Brickseek and couldn't do it.
Brickseek has a "Easy Buy" where you can add items to your list and have it find sellers, but it didn't work at all for me. Manually trying to find each piece is not worth the effort.
You buy or just get donated legos from people that no longer use them and then you can sell custom sets for people by running through the semi sorted bins and creating the order. So you don't want to sell the machine but rather, sell Legos. Perhaps the main issue is whether resale rights are allowed but seems solvable.
I would suspect this is a nice little business selling 40% discounted complete Lego sets.