The BBS methods of accessing adult content did come first.
The oldest paysite might be "The Ranch and Cattle Bunkhouse" at bunkhouse.com ... created back in 1995 and operated as a BBS before that. No longer a paysite these days.
There may be others even older that I'm not remembering.
Good times.
P.S. Our own original paysite was inside our 1stSmokeshop.com cigar emporium website back in 1996. That "XXX Smokeshop" adult section was rolled out onto several paysite domains a year later. There was a BBS we did that preceded the Smokeshop too.