Little caution here on the term topsoil.. I run a dump-truck - hauling to different contractors.. I service 5 different landscape companies within my customer base.
They each call for topsoil occasionally but they each want something different by the use of that term.
As you buy this make real sure you and the person selling or filling your order are on the same mindset...
The other part of your question.. Finished black compost is a good raised bed media. Carefull on planting tall stuff if the wind may move it around. Stake it and tie it for stability.

"Topsoil" is simply the top 4 to 6 inches of soil from someplace, so it may well be something decent or it could be simply garbage. Most everyone has in mind that "topsoil" is loam, but since there is not enough loam available not all "topsoil" can be.
Stick with compost to amend the soil you have or to fill a raised bed. Lasagna gardening plants in organic matter and I have used compost as potting soil with no problems for many years now, as have many others.

I sell compost. I myself never recommend using compost as a stand alone growing media to anyone buying from me. I recommend that my compost be used as a soil amendment, either incorporating it into an existing soil or as a mulch/top dressing.

Lloyd

Like Lloyd, I never recommend compost as a stand alone planting medium either. While it is a great addition to a raised bed soil mix, you should also have a mineral based soil component.

If you need the material trucked in anyway, check with your suppliers for anything called a 3-way planting mix or garden planting mix or something similar. Or settle for the 'topsoil', whatever that may be -- but have it combined with the compost as a combo delivery. Somewhere in the neighborhood or 75% soil, 25% compost is great but you could increase the compost component if desired. Just be prepared for more shrinkage of material with the more compost included.

Most all potting soil mixes I have seen are peat moss, finely ground bark, coir, or a combination of those with some perlite or vermiculite added for drainage and maybe some kind of synthetic fertilizer. Since you are then planting in a growing medium that is only organic matter why would compost not work as well?

No one on this thread has said planting in nothing but compost would not work, no one.

Heck, one can grow plants hydroponically if one wishes but that wasn't the question.

Lloyd

kimmsr, you are comparing apples to oranges. Potting mixes have been designed for growing in containers.......a very different situation with very different requirements compared inground gardening or even raised beds. And even with container gardening, compost is not recommended as a medium or even a substantial component, simply because it doesn't have the durability of the other materials, will continue to degrade and collapse and eventually compromise drainage, which is the paramount concern of container gardening.

Compost is not a soil - it is an additive or amendment.

It's still a case of buyer beware.
I bought two loads of 'Triple mix' from our local garden center. The first load was good, really helped the garden. Second load nothing would grow in it, not even grass seed!
Tried to get some satisfaction from the suppliers, but all I got was a stone wall.
Needless to say, won't go there again, and all my friends got to know about it.

Word of mouth is the best saleman in the world.
I have grown tomatoes in rotted cow manure & hay, a year after the cows were sold off the feed lot.
Give me a break here, I was only 16 year old & did not know any better. Point is that they were the best tomatoes I have grown in 42 years of gardening, I had tomatoes fresh from the vine in Novmber, that year.
But I can not know what you are calling compost.