Nothing makes me feel old like having a game I used to play as a teenager being the topic of an r/askhistorians thread.

Anyway, these are the requirements for the original shareware version of Doom:

DOOM(TM) requires an IBM compatible 386 or better with 4 megs of RAM, a VGA graphics card, and a hard disk drive. A 486 or better, a Sound Blaster Pro(TM) or 100% compatible sound card is recommended. A network that uses the IPX protocol is required for network gameplay.

Source: http://www.classicdoom.com/doominfo.htm

So since we are totally radical gamerz, we are mostly likely going to purchase a 486 to get max cowabunga frames.

Here are some adds for 486 pcs from 1993 (pages 78-79):

https://books.google.com.au/books?id=4RN8nH8oZ2QC&pg=PA112&lpg=PA112&dq=486+pc+cost&source=bl&ots=3Os5QRIgk2&sig=XS4b2JQNFX7mdAmiL1kwu0lixhI&hl=en&sa=X&ved=0ahUKEwjkytD2y-XMAhVEJ6YKHde8A_wQ6AEIRzAH#v=onepage&q=486%20pc%20cost&f=false

The prices range from $1499 for a 486/SX at 25 megahertz and 4 megabytes of ram to the most tubular 486/DX2 at 50 megahertz and 8 meg of ram with 512k video memory, all from $2699.

Hope that helps!