First, let me start by saying that large zoom multipliers are specifically for consumers and NOT for professionals. No self-resepcting professional would be caught dead with a super-zoom on their camera. Superzooms are great for convenience, but they have to make major compromises in terms of image quality. If a professional needs to be able to rapidly switch between wide angle and telephoto, then they use two cameras. One with a wide angle lens and one with a telephoto.

As to how so many features can be included so cheaply, it really comes down to quality and speed. 1080p is really a pretty standard feature these days and 12 megapixels is not particularly high anymore in terms of megapixel count. It has a cheap lens that only reaches f/3.5 at the most open on the wide end and is only f/5.8 on the long end which is quite slow. The ISO range isn't all that great either, so it won't handle low light particularly well. It is limited to a relatively slow 1/1600 shutter speed.

It is also worth pointing out that when compared to your S95, the SX510 has a much smaller sensor. Smaller sensors are generally cheaper to manufacture since they have a smaller surface area (and thus less likely to get defects ruining a lot of material). They also allow usage of cheaper lenses because they don't need as large of an image circle (the area of light that is passed through to the sensor.) This also limits the camera since it runs in to issues with diffraction more quickly (occurs when you focus light on small spots) and also can't produce as shallow of a depth of field (background blur pretty much impossible, although that is still true of most point and shoots).

Is it a good camera, certainly for the price, but it is also far from the best around if you don't consider price. It is a jack of all trades camera that compromises a little bit in a lot of places. It lets it give a nice feature set at a relatively low price, but it limits the depth of capability in any one area.

Also, I noticed you mentioned SLRs in your question. Do note that this camera is NOT an SLR or a system camera. It is a super-zoom point and shoot. The lens is not removable and it goes directly to the sensor. You can only view what you are pointing at via the screen, not a view finder.