You might compare it to something they can see and if possible, use everyday.
For example, the automobile. Cars started as much less refined and reliable devices than we have today. While cars have been made for over 100 years, but software probably about half that long. Cars are available with significant customization, some included in the price (like choice of color), others like engine size, transmission type, wheel/tire, trim level are significant cost drivers.
There are many feature, quality, and cost drivers for cars, and for software. Then you can discuss how software technology, availability of expertise, maybe even where it is built will make a big difference. Appropriately development cycles (for example, yearly models with small changes, body/engine/platform changes about every three years) are driven by a combination of customer needs and a complex design process. Some products start small and dumpy looking (think of the Honda Accord), but get improved every year until they are top rated.
Cars have recalls (often way more costly than software upgrades) and incremental improvements in the form of running changes to their parts lists (think bug fixes), and often they need long term support (think backward/forward compatibility). Much of the cost of your car comes after you drive it home. Much of the software cost comes after the initial product release as you update and upgrade customers.
In some cases, you can reference well known products that include software or other software products. For example, phones have a release cycle and updates and methods of adding functionality after the initial sale to build more revenue. Phones are a great illustration of forward / backward compatibility. Too much, and people won't dump the old one to buy a new one. Too little, and customers get desperate to have a phone they won't hate before its contract is up.
Products like Windows, Microsoft Office, web browsers, and web pages are all software that can be used in discussions. They have been updated on annual or three year cycles, but may have automatic updates more frequently. They have bugs and security holes that affect customers to varied degrees, but are a part of the landscape despite our best efforts. Customers can get fixes free, but generally pay for enhancements, often as a bundle, sometimes as an individual module or via an licence key.
Industry leaders like Microsoft, Apple, Google, and Amazon all deliver relatively inexpensive customers to users. But they have huge expenses that enabled those products. Their experience shows that software is expensive, but valuable and profitable. They often compromise between quality, having all the features they want, and getting into markets when the timing is right. Not every product they make is a success, and they sometimes turn dogs into winners by renaming, improved marketing and sales, or cutting their losses and using what they learned in later products.