Save your money. It might last minutes or hours, but no way will it even last a year unless it's simply not used.

We had an old tub reglazed in our last house (the tub was probably ca 1920 or so?) and I have to say, although the job was a bear (even with a professional firm doing it), it did last a good 15 years before we saw any finish blemishes at all. And that was with daily use. However, I cannot even begin to imagine how one could do a remotely reasonable job as a DIY. The company that did it had to do some fairy exhaustive prep work, then the tub was sprayed (about 6 or 7 times). In the end, it was beautiful -- but it was a lengthy process that I wouldn't dream of undertaking as an individual. We are about to have a 1959-era tub reglazed in our current home, and the estimates we've gotten are in the $600-$800 range, so I don't think the estimate is excessive. Get it done professionally (after checking the firm's references CAREFULLY -- there are good reglazers, and bad reglazers.) Be sure you talk to references. But absolutely no way, in my opinion, that you can do it properly yourself.