estimating value of type-in traffic

In my experience, industry keyword phrases are married to keyword search and therefore are married - to some degree - with direct navigation. It's common sense at work: If a popular generic phrase within an industry is "blue velvet widgets" there will be a direct navigation activity as well as that specific phrase appearing in the SERPs.

Start keyword search via industry channels.

Exceptions need to be made for highly spammed subjects.

Whilst I'd love to know traffic levels before registering a domain I tend not to sweat that issue and instead I focus on the converted-lead value to an enduser of direct navigation traffic and on the prospect of market growth for a traffic-targeting domain.

In layman's terms, if FuzzyBlueWidgets.com only gets 3 type-ins a year BUT if the sale of a FBW results in a $10,000.00 commission AND IF one of those visitors were to consume/purchase/lease/hire/whatever a FBW what is the value of that domain and it's traffic?

You might get 10,000 visits to a popular joke or stupidity domain and that domain might make $1,000/year versus 3 visits and $10,000/year. Which is the better traffic domain?

Keep in mind that domain parking may not make you $10,000/year but that may not be your end game. At some point, some savvy new entrant to the wonders of WWW traffic, may awaken to the idea that the domain you hold may produce very targeted and profitable traffic. To THAT enduser what is a domain that yields $10,000/year likely worth?

You may have to wait awhile. You may have to employ interim measures to increase your yield - such as offering a lead-gen partnership. You may wish to increase traffic by building a microsite and then, in time, flipping the site to an enduser-consumer of that traffic.

Traffic volume is only one factor to consider.