The decaf process seems expensive so you might expect the end result to cost more, but it never does. Which means either the producers are making less profit on decaf, or they are using lower quality beans. If the latter is true, which seems more likely, that might explain why decaf sometimes tastes less good, separately from the effect of the process itself on taste.
The same decaf coffee is more expensive. The producers decaffeinate their lesser coffees. But you've hit on why the "sugar-cane method" i.e. the solvent based approach produces better coffee. It's possible for it to be done at origin and so the actual coffee producers can choose what coffee to decaffeinate and can absorb some of the additional costs in the "processing" stage while using higher quality coffee in the process.