You could do more to get the potential customer comfortable with your product. 7 days and $50 is a lot to request of people, when there is competition for this service. It looks like one of those competing tools was created by you,
http://impossibility.org . And for full disclosure, I am working on a domain name suggestion tool too:
http://domainjig.comDuring testing, I learned that many different opinions exist about what makes a good domain name. So while you may have settled the matter in your own head, you should take care to set expectations for your customers. A quick list of domains you think are good (perhaps also domains you think are not good) would help people see if they agree with your priorities.
For instance, I've heard differing opinions about the importance of these characteristics:
.com only vs other Top Level Domains
fewer characters vs simpler concepts
distribution mechanisms: SEO, ads, word of mouth
misspellings, or non-obvious spellings
similar style to recent successful startups
country-specific registrar risk
combine TLD letters into the word
non-english languages
adjective + noun
rhyming / puns
describes the product and/or a tone
As an example, this article describes priorities baked-in to the domain name suggestion tool at domainjig.com : http://domainjig.com/ideas/great-domain-names.html
btw, I like the eyebrow raise on mouseover.