Interesting topic - especially as the starting point is an argument from the late, great, Tommy Wonder!
I normally shy away from putting the words "art" and "magic" together - not because that's wrong, just because I think it sounds overly pompous. However, I'm about to just that, quite a bit, in this post.
When people talk about magic as an art, I think we have to remember that there's a few different levels to that artistry.
The Technical Artist
Art can be defined as "The principles or methods governing any craft or branch of learning"; as such, any magician who is sufficiently capable in executing the methods of magic could well be considered to be an artist. Any painter who is accomplished enough to produce a copy of a Van Gogh painting would be considered an artist as well - the fact that they haven't created anything is, in this context, irrelevant. Therefore, there is indeed merit - and artistry - to buying, practising and perfecting the tricks of others.
The Performance Artist
Magic is also a "performance art". In this subject I believe I can speak with some authority, being not only a working magician but also the director of a dance and performing arts company. Performance art is, again, nothing to do with creativity. Consider a classical pianist performing one of Mozart's concertos, or a ballet company performing Swan Lake - I think you'd struggle to find support for the argument that they're not artists! I'm talking about the art of being able to engage an audience, which can be considered as a collection of skills and knowledge which is shared by all the various media that can be presented as a performance (dance, music, magic...). Of course, it is important that you are sufficiently skilled in your chosen medium, which takes us back to the first definition mentioned above.
The Creative Artist
Finally, art can be defined as the production or creation of something which is beautiful or appealing, or significant. The creation of magic tricks is indeed a form of art (however frivolous!) - however, not one which is necessarily "better" than the others - in fact, the others are more important! As some posters have pointed out, a prerequisite for creating art is understanding the required technique; one must be a "technical artist" first. I also believe that it is critical that you should have a great deal of performing experience before you are able to create magic that will engage an audience - you must be a "performance artist" as well. After that, if you are willing to put in the time and effort, and have a creative mind, you should be able to become a "creative artist" as well.
Why buy tricks? Because learning magic is fun and rewarding - and for many of us, that's plenty. For those of us aspiring to "art", this is also sufficient provided that you work hard enough. Once you have mastered the tricks that you have bought, you can then go out and start performing them - keep on performing and learning from your mistakes long enough, and you may well become a performance artist as well.
Cheers,
David.