In a word? Cost.
At the time of the 1200's release, the 030 in any variant was exorbitant. When the 030 accelerators first came out, they weren't a whole lot less than the price of a new A1200. As for the 060... Oh good lord. Do you remember the costs of accelerators fitted with those things even in 1998?! ROTFL.
Because the 030 hadn't even been released until after the A500 was in full production. And again, cost, at the time the 030 would have been so fresh it would have been warm still by the time it was delivered. The A500 was designed to fit within a budget, adding even an 020 as an option at the time of launch would have been hideously expensive. Remember the costs of the A3000 when it was launched? I do.
No different to a PC of the day. And the PC, trust me was crap. I priced out like for like before I bought my Amiga 1200 in 1993 and the PC was more expensive. And having experienced a PC of the day trust me you didn`t want to go there.
Computing in those days was very expensive. What ever you ran. The Amiga was way ahead of its competitors in multitasking, animations etc and thats why. The Amiga though was the only model that let you start modest and build to your own pace. Unlike the tinboxes and Macs of the day.
As for 1998 ....
By 1998 the market of supply and demand was such that because of the falling user base the makers of the 060 had to lift the price to stay alive. Personally I would still pay those prices now if I could get a new Cyberstorm.... ar hum.
scuzz
http://www.commodore-amiga-retro.com