Money wise, you save or break even.

This is false. Unless you eat steak or other expensive meats on a regular basis, meat is quite cheap. For example, my meat consumption is mostly chicken, assorted processed meats (salamis, frankfurters, and other sorts of sausages, mainly, but also things like pelmeni), fish (not the expensive kind), and the occasional pork (canned) and beef (cheap cuts). None of these things are pricy; I am getting a lot of protein (and fat and other good/necessary stuff) for my money.

It has no time cost in much of the US (most restaurants have vegetarian options).

Do you eat at restaurants all the time? Learning how to cook the new things you're now eating instead of meat is a time cost.

Also, there are costs you don't mention: for instance, a sudden, radical change in diet may have unforeseen health consequences. If the transition causes me to feel hungry all the time, that would be disastrous; hunger has an extreme negative effect on my mental performance, and as a software engineer, that is not the slightest bit acceptable. Furthermore, for someone with food allergies, like me, trying new foods is not without risk.

it can be applied to every change one might possibly make in one's behavior.

And it would be correct to deny that a change that would possibly be made to one's behavior is "such a cheap change" that we don't need to weigh the cost of the change very much.

Your discounting of non-human life has to be rather extreme for "I will have to remind myself to change my behavior" to out weigh an immediate, direct and calculable reduction in world suffering.

That only applies to someone who already agrees with you about animal suffering to a sufficient degree that he should just become a vegetarian immediately anyway. Otherwise it's not all that calculable.