I'm all about being cheap, but there are some things you just shouldn't do to save money, and one of those is to try to save money by buying the cheaper, more well-known sunscreens.
In a review of almost a thousand sunscreens, only 14% passed safety standards and were considered safe and protective enough to use by the The Evironmental Working Group
The three major leading brands, Banana Boat, Neutrogena, and Coppertone were among the worst culprits. Safety issues range from lack of UVA protection, dangerous chemicals, ingredients that breakdown IN THE SUN, and other dangers.
For a list of safe sunscreens, visit the Environmental Working Group's site, by following the link above.