There is a big difference between "cheap" and "on a budget". Things on the second category may be unexpensive but not necessary cheap, that implies not only a level of money expended but a level of 'production'.
The ad below is a good example of something done 'on a budget'. When it comes to advertising if you have to work with very small resources, the basic idea behind the commercial is key. At the end of the day, is easy to be able to do something memorable if you have millions. Good creatives shine when they are presented with the challenge of small budgets.
This commercial from Tony Jaffe for Taylor Rental, is a good example of "unexpensive":
Simple, funny and unexpensive but not cheap. Check more of his work and his classics, here.