All you want is just to offer your services at a reasonable rate, but heh!, when people hear that the software is free, they do not see the need of you. So in the end you have a hard time explaining that you as a better informed expert can help the client saves money and effort and heartaches.
But no, the word 'free' has corrupted their minds. They expected even your time to be free, and demand you to give them pre-sales or presentation or even prototype as if you have SAP or IBM that pays your salary.
Thus i come to the conclusion that it is all a matter of salesmanship. You just need to have the best sales know-how you can find. Try googling for "art of negotiation" and "art of salesmanship".
I came across this 'Peeler Salesman' who could sell something that at first thought no one would wana buy. It is like selling ice to eskimos. But then we do buy bottled water don't we? So do learn more salesmanship whenever you can. It could be that you are just a bad salesman at selling yourself.
Here are some thought-provoking links: