Whilst these 'Dollies' help solve some of the issues associated with trying to live with such an enormous, heavy bust, much like the Daleks in Doctor Who, steps will still be somewhat of a challenge!
Oddball sci-fi references aside, steps or stairs are probably not a super-high priority when your breasts are this enormous - not in the grand scheme of things, anyway. That's where these relatively simple 'Dollies' come in. They are the difference between struggling to move, or even stand, and clawing back some basic mobility and independence. When breasts start developing beyond the limits of even the strongest and most determined of bearers, these Dollies (or a singular Dolly - initially one could be used, attached to the bras gore until more substantial support was required at larger sizes) make a world of difference to what is achievable by the human body.
Of course, they have some downsides; they are compartively cheap, as far as supportive equipment goes at this size, but they are also static - in other words, you still need something to lift the breasts in order to attach them to the Dolly - a hoist of lift or somesuch. Because the units are independent, they can also 'buck' and 'pull' as the castors reorientate themselves, and they can have a reputation to be unstable, expecially at larger sizes, and although it is possible to increase the width of the bases, doing so also increases the width needed for the entire person to remain mobile. That extra few inches can mean all the difference between making it through an opening, or not.
This opportunity to look at the back of such a huge bra also helps us better consider the sheer enormity of the challenges faced. For example, they say that around 75 to 85 percent of the bras load should be carried by the band, around the torso. As you can see though, there is simply no way that such a modest frame can be expected to support so much breast. As you can see, the bodily real-estate available is utilised as much as reasonably possible, but at sizes such as this, extra support is essential...