One look and it's easy to recognize how much more goes into a sale than a few key fields. Currency, tax jurisdiction, multiple items on a single sales invoice, shipment tracking, discounting and so on. Good business tools help you adhere to straightforward business practices. QuickBooks for example is the industry standard in accounting because it models accounting so perfectly.
Still, why so much more for a product like this? The bottom line in software development is the more features you support, the more expensive your product is to maintain - it just costs more to make artsystems products. Artworkarchive.com can offer a lower pricing tier because their product does fewer things - the surface area of things to debug, refactor and regression test when you add something new is just much smaller (and therefore cheaper) to support. There's no wrong answer in pricing, and essentially these are two different products for different ends of the market.
I think the key takeaway here is that if your studio practice is generating a significant amount of sales or management overhead, you may want to look at a robust business management package like StudioPro. If you just need a simple way to organize your studio and manage sales (or like a streamlined experience) ArtworkArchive.com is probably the way to go.
Other Paid Solutions
There are lots of other options out there that, frankly, I haven't done research on. The following two cloud based solutions are priced in the mid-range and probably offer more features than artworkarchive.com - and less than artsystems.
Masterpiece Manager - cloud based, $19/month - I see this one recommended quite a bit.
Artcloud - cloud based, $19/month
I'll make the obvious point here that Google Sheets can be used for all of this if you don't mind keeping track of things in a very manual, list oriented way.
But if you're looking for a target application in the free software space, there appear to be options. I haven't dug into them yet so will save that for a followup post. Here's what I'll be looking at (so far). Let me know if I should look at anything else!