Question re: not attending a wedding.

DH & I decided that we were going to have to turn down some wedding invitations since it can be very expensive to attend alot of weddings. We just can't afford it with a mortgage, one salary, one child and another on the way. I mean, I would never not attend a close friend or family member's wedding but we have to draw the line somewhere.

We received an invite from a guy in my DH's firehouse for his wedding. First, my DH just got transferred to that house about 2 months ago and he doesnt really know the guy too well, I'm not even sure if he knew the guy was getting married. He was surprised to receive the invite. My DH is his superior so I said he probably didnt know what's the proper etiquette and didnt want to insult the officers in the house and invited them. Or for all I know, they are the type who invite EVERYONE to their wedding.

So here's my question...we are not going to attend but are we supposed to send a gift? With my wedding, we had some people not attend who did send a gift and some who didnt so I'm not sure. Plus we knew all those guests, which is different from this situation.

Anyone up on the etiquette as to sending a gift? On one hand, I really don't feel like putting out money for people I dont even know just because they decided to add us to their guest list (and truthfully can't really afford to spend) but on the other hand, I don't want to be cheap either.

Thanks!