“This is very believable if they retain outside developers or keep ongoing support available.”
What, if any, new development has occurred over the past 20 years? There’s no mobile app to support either.
I do think some of the estimates are a bit high based on the fact that technology has changed, however, their #'s still really aren't out of bounds. The biggest expense is people power, which is still very well within absolutely reasonable bounds for a 1 - 2 man operation.