Hi M - I was recently looking for a new tank so I was comparing prices as I was very insistant that I wanted bowfront! I love bowfronts! They actually amplify fish viewing! ( I suppose a plastic version might actaully distort the view.. ) That is why I wanted one! My little tanks are all bowfronts and I really enjoy see the fish so well - that said, they are also all acrylic tanks which is another dimension... and acrylic bowfront is the dream of dreams!

(for me, anyway)!
Bowfront tanks do cost more becuase of the workmanship and design that go into creating such a shape to contain that weight of water. But, bowfornts can be made in both glass and acrylic - glass being the less expensive version of the already more expensive shape... However, companies that produce high grade glass aquaria make some very beautiful bowfronts that are absolutely no less spectacular in viewing than acrylic!
In pricing out bowfornts, I find that in glass or acrylic, they are usually a third more to double the price of the same size rectangular tank. Getting a combo is a good option as it is usually the best deal - combos usually include hood and lighting system (not the bulbs). Chenk to make sure whether the term combo includes the stand or not - it does not always (often), even if the tank is shown on one!
Make sure of the measurements of the bowfornt before buying or adding it to an existing stand - even if it is glass, because of the shape, you would want to make sure that all of it is sitting on a flat surface!
I found that comparing online prices to store prices gave me the best feel for how good was the deal.. on line you have to consider shipping charges and most good aquatic stores will insist on giving you a shipping quote before allowing the purchase. At stores, you don't have a shipping charge but greater mark-up to cover their over-head - so, when comparing, take the overall price at each location and take and average - then you should come up with a reasonable price.