You've answered your own question. They are low-volume, almost custom-made equipment, hence the high cost. There are $4000-$5000 road bikes and MTBs for that matter - for the same reasons.
There's also the chicken-vs.-egg quandry: No big bike company is willing to crank out large numbers of recumbents when market demand is so very limited but demand will never increase until the public is exposed to large numbers of affordable product. Only Cannondale has a recumbent - it is expensive and in limited distribution. Trek's short foray into recumbents was a failure.
Lower cost recumbents are available in the $600-$900 range - many of these suitable to first-time bent riders. Compared to a $90 big-box store bike, that's expensive, but you can find many bikes in your local bike shop fin the $600-$900 range or higher.
Educate yourself on-line and try to locate some bents to ride. You may find a used one for less outlay. If you get hooked, the apparent price is not going to seem so high after all.
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Good night and joy be with you all.