I still have a Seagate ST4096 5'25" full height MFM controller and a whopping 80(!!!) Megabyte.. 
Was a real modern drive, instead of a stepper motor it had a voice coil actuator,
Next up is a ST4026, 5'25" full height 20 Mb also with a voice coil actuator
Oh and a 10M Seagate ST412 also 5.25" full height MFM 10Mb of course this one was stepper motor driven.
They all work fine, the ST412 is from 1983 and works like sunshine.
Next to those I've got a whole boat load of Seagate ST225's they're indestructible.. 21M 5.25" half height so the size of a CD-ROM drive.
Besides the problem of cramming more and more data onto platters the other problem is being able to position the read/write heads accurate enough, the stepper motor had a table which told it to step an x amount to find a track, because of the platters expanding and contracting again due to warmth or cold they sometimes were unable to find a track and report an error.
Voice coil actuators are more stupid, they have no clue where they are at all so in those old drives you actually had an extra platter with the track info encoded into it so the actuator would know where it was.
As for drives getting cheaper, yes some.. my 4096 is now between 500 and 700 Euro's worth..

Was a real modern drive, instead of a stepper motor it had a voice coil actuator,
Next up is a ST4026, 5'25" full height 20 Mb also with a voice coil actuator
Oh and a 10M Seagate ST412 also 5.25" full height MFM 10Mb of course this one was stepper motor driven.
They all work fine, the ST412 is from 1983 and works like sunshine.
Next to those I've got a whole boat load of Seagate ST225's they're indestructible.. 21M 5.25" half height so the size of a CD-ROM drive.
Besides the problem of cramming more and more data onto platters the other problem is being able to position the read/write heads accurate enough, the stepper motor had a table which told it to step an x amount to find a track, because of the platters expanding and contracting again due to warmth or cold they sometimes were unable to find a track and report an error.
Voice coil actuators are more stupid, they have no clue where they are at all so in those old drives you actually had an extra platter with the track info encoded into it so the actuator would know where it was.
As for drives getting cheaper, yes some.. my 4096 is now between 500 and 700 Euro's worth..
