The post not making any sense suggests it's facetious, but taking it at face value, it reads as "Well, I was going to invite you to my birthday party, but now I'm not!"
Or more 'Well I was going to charge you to come to my birthday party'. Either as a serious statement or being a bit silly I really have no idea what they hope to achieve, especially in all places like SPUF. Saying that of course I do, that's the main content of half the posts there.