Strange upgrading policy

It was really the best spreadsheet software for iPhone (I own the Numbers too, and have tried many other programs), but recently two things happened:
- my spreadsheet file (consisting of 5 sheets) refused to calculate formulas - I had to revert to old copy and manually rewrite all new data;
- the app authors (Mariner Software) prepared a universal version of the app, calling it Calc XLS, which version is 4.0, but they left Mariner Calc at version 3.9. Arent owners of 3.9 entitled to 4.0 upgrade? Why I have to shell out 5,49€ again, to not be left with old erroneous version?

RomanHA about Mariner Calc Spreadsheet for iPhone, v3.9.0