This may come as a surprise to you (and the baboons on Faux news), but the President does not make every single decision that is made in the Federal government. The selection of website developers wad made by planners within the Dept of Health & Human Services after a public bidding process as required by federal law. (Unlike the billions in no-bid contracts given to Dick Cheyney's friends under the Bush administration.)
Amazon could have done the website and at a much cheaper amount. But no-bids are sometimes done because it rewards a relationship, or because of unique expertise, or security issues, or sometimes because of timing. In this case, we will undoubtably have many reasons to investigate this and in excruciating detail.