Probably they wouldn't get 'mass adoption' with lower prices either. Devtools is a niche market and for an independent company it is difficult.
See for example the price for VA Smalltalk...: $6995 for a new developer license.
https://www.instantiations.com/products/purchase.html
Or VisualWorks, which charges based on either end users, number of CPUs, or a royalty basis.
It's a special niche market and in the Lisp space there are unfortunately no companies left of those which once sold actively maintained mid-priced Lisp systems with actual GUI Libs/IDEs (Dead/sold/abandoned/unmaintained: Procyon CL, Expertelligence ExperLisp, Corman CL, Digitool's MCL, Golden Common Lisp from Gold Hill, ...).
The remaining ones are two of the higher-priced vendors: Allegro CL and LispWorks. There were attempts to offer commercial CL systems - but none with emphasis on GUI (example Scieneer CL).
They're probably serving their existing customers well, since they're still around, but I doubt they're getting many new customers (or mass adoption) with these prices: http://www.lispworks.com/buy/prices-2c.html, https://franz.com/products/packages/.