I agree 100%.
Sorry if $150 is too much, they have places that pay you money every week! Its crazy. Supporting your own product by investing in it maybe a crazy idea, but, if you wont, no one else will.
Anyways - like Ryan said, stand your ground. Who cares if you sell 100 or 10 million copies? They aint got shizz to say about it. Dont lower your worth because someone cant afford $150 for DAYS of time saving work