Sounds like your husband has a great way to earn some extra money. I have written a few poems here and there in my life but have never thought about selling poems.
As far as the pricing goes, it is going to depend on who you market to. Not everyone I know would be willing to pay for a poem but if you find the right market, you will be able to adjust your prices accordingly.
Like I said, I am not experienced in writing poems, but when it comes to writing or providing any creative service, one helpful thing I have learned is never to undercut yourself.
Your time is valuable and while not everyone will appreciate it enough to pay the price you expect, you never want to go so cheap that you undervalue your work.
I wish you the best in your endeavor!