The phrase upwards of X appears to be defined very explicitly to mean simply and only “more than X”. (In other words, it is an exact substitute for “north of”.)
I have a pernicious and deeply held understanding of the phrase as meaning “as much as X, but not more” or “trending upwards towards X” (in both of these cases, the quantity in question is understood to be slightly less than or maybe equal to X).
This is not merely a one-off personal error. I have informally polled family and friends, and have also polled 100+ people on Twitter, and it's clear that the understanding I have is common, if not the dominant understanding of the phrase.
I'm an American New Englander by upbringing, but I'm not sure what other context is useful. I have immediate family that swears by the dictionary definition, and others who are with me on this.
I'd be less interested if these were shades of meaning, but these are clear opposites of definition. Does anyone know what the distinction is in regions/dialects, or otherwise where this phrase comes from?