Choosing between a .com hyphenated domain name and a non .com without a hyphen

My website is going to be about technical tutorials/stuff and later I also plan to release an ebook. It's very focused on an important technical topic. The best domain possible is composed to 2 words. Let's say WordA and WordB. Google keyword tool reports global 550,000 searches for "WordA WordB" and "WordA-WordB" per month. Here is the situation:

1. WordAWordB.com and .net are already booked and being sold for horrible amount on GoDaddy. .org is registered but no website. I managed to register "WordAWordB.in" domain.
2. "WordA-WordB.com" (with hyphen) is on sale on godaddy for around $250. WordA-WordB.net is available for registration.
3. Just to add, I managed to register "WordAWordC.com". WordC is related to WordB in technical terms. But, "WordA WordC" has global monthly search of around 15,000.

I cannot buy WordAWordB.com or .net as they are very expensive. Should I buy WordA-WordB.com and also register .net version. Or, should I use "WordAWordB.in" to build my website? I wonder if hyphens are good in my case.