For obvious reasons, progress made, (money earned, ships bought, etc.), is reset for every new Alpha release.
I queried when this progress resetting is likely to stop, on the Official Frontier Forums, and received a very quick reply from Michael Brookes (Executive Producer). He states, “You should expect progress to be reset at various stages within the beta process. Once we reach gamma we will endeavour to not reset unless we have to.”
Good to know, before I dive into the Premium Beta, come May 30th!