I suspect all the signs were done by one person. My guess is he tried to make the "handwriting" (spraypaintwriting?) different, but there is a certain larger similarity amongst the characters from the three signs. The white poster suggests to me that this is a clever ad from a print shop, perhaps targeting a rural clientele.
You may be right. This setup looks like a play on the phrase "dirt cheap." However, the professional sign does not give the name of a business nor contact information.
Disclaimer: I am not affiliated with any sign company.
Jeanette Isabelle