Individual lessons may be inexpensive, but they wind up being a chunk of change in aggregate. Putting money into lessons when I'm not absolutely sure I'll keep going with it is pretty foolish. A few lessons after I've made progress and proved my "sticktoitiveness" might be useful, but that's a ways off.

Also, in this case, I may have a choice. Let's say I do pick it up and stay serious with it. The guitar I have is certainly good enough to start with. And while I could work with it indefinitely, if I find I'm really going to continue long-term, I'm probably going to strongly want to drop some cash into a full sized instrument. That'd be far easier if I take the inexpensive (if longer and harder) route to learning.