Funny, I was going to write a blog post about this after a friend accused me of being too cheap in an insulting manner! To me, the difference between cheap and frugal is connotation. When I think of people being cheap I think of people who undertip servers, people who will save money at the expense of others, people whose enjoyment of life is stunted. To me, being frugal means the judicious use of my time and money.
Having money in the bank because I am frugal has allowed me to lend/give money to people I love who are going through hard times. I think if I was cheap I would just hoard it but because I think of my frugality as a way to be able to live my life my way, my way also means helping others.
When my friend told me I was being too cheap I pointed out to her that my being cheap enabled me to host these fun tea parties - of which she was currently attending - because it brought me joy to spend on my friends & have us all together. A cheap person I don't see as someone who shares but instead as someone who hoards.