The assumptions of this question are at best misleading and maybe based on personal experience, but not the situation at the time cited.
As requested I just pulled out the very second issue of Kilobaud Magazin of February 1977 (*1).
Right at the beginning there is an ad on page 12 selling ASR33 starting at USD 840. Page 54 shows an ad offering an Olivetti teletype at USD 950, even including RS232. The same ad also features a 100 LPM 132 column dot matrix printer at the same price. So why buy a slow 10 CPS teletype? The same ad also features a thermal printer at USD 475.
Next, page 130 features a rather high quality (compared to an ASR33) IBM Selectric with RS232 at USD 895. It might be useful to remember that the Selectric wasn't developed primarily as a typewriter, but as printing terminal for mainframe usage. It's not their developers' fault that it was also a darn durable office typewriter. They just made a reliable device with no hard connection between the keyboard and print mechanism.
Finally page 49 shows how cheap dot matrix already was in the spring of 1977, with an ad for a printer with a parallel port at USD 425 - when bought as kit (just electronics and print mechanics) it got down to only USD 179. It's also interesting here that a current loop (50mA) version, as a TTY replacement, was rather expensive at USD 575. This would not only mean one has to pay for an additional current loop interface in the computer (not available by default on most computers), but also pay even more for the printer itself. Ok, still less than a full teletype, but why?
Kilobaud was always a magazine directed at the hobbyist, not business or large users, attracting advertisers targeting a low price range. I bet pulling any other magazine from the same time will show a similar result. Even more so after 1977.
Proof#1 - Already in the spring of 1977, at the very start of microcomputer usage, shows that dot matrix printers were not only widely available, but also undercut TTYs by a large amount.
So lets take a peek at the February 1981 issue of the same magazine. That's about 7 months before the IBM PC debuted in August 1981 and thus DOS. Here it is easy to see that dot matrix printers and the parallel port have completely taken over. Page 11 features an ad with Epson's MX-70 at USD 645 and its 'brother' MX-80 for USD 800. Another ad at page 24 (*2) gives a nice comparison. here an MX-80 is only USD 575, while a Centronics 730 costs USD 599.
There are many more featuring various dot matrix printers in the range of USD 400 to 800, but only a single one featuring a (Type 43) Teletype on page 41 - still at USD 989. So while TTY stayed basically the same over this 4 year period, dot matrix printers did not only improve but dropped quite a lot in price. Oh, and a 13 column (!) Selectric with parallel interface is down to competitive USD 659 (p.71).
This is of course only one magazine and two issues, but I'm quite sure this snap sample will hold when checking more data from other sources during the time period.
Proof#2 - By 1981 the dot matrix printer had complete victory and teletypes where merely an outdated and expensive side note.
Of course, there were many articles in these early magazines to convert some TTY, electric typewriter or Etch-a-Sketches to a hardcopy devices. As much as there were even more articles about building your own computer from parts or writing an OS from scratch.
And yes, for hobbyists with too much time on their hands, finding a TTY in a scrap sale was still a feasible idea for the fun alone, but it for sure was never anywhere near mainstream.
Conclusion: The claim of teletypes being the 'most common' printer before DOS never existed in the first place.
Last but not least, considering the above claim, the PC (and DOS) in 1981 was meant for professional use, not as a hobbyist toy. But even with the clearly made for hacking Apple II the first interface was parallel, and the first printer offered by Apple (in 1978), targeted at hobbyists was a (thermal) matrix printer - undercutting any TTY price by far.
Having said all of this, there are special occasions where even in 1980 new development for TTY was a thing. In my case I had already an Apple II (and a cheap dot matrix printer) in Spring of 1980 when I joined the Bundeswehr (German Army). Due to some less than official circumstances it worked out that we used my Apple to improve some bureaucracy during my service - and to produce printout I did build an interface so three(!) TTY could be connected to print in parallel. After all, they were dead slow, so it was better to have three interleaving print jobs and merge the pages later on, than to wait three times as long doing the same on a single TTY. This was also quite some fun to program :))
The reason was less technical or due to budget but rather availability. As part of the staff of a signaling battalion TTYs were available by the dozen :))
*1 - Which is BTW the issue featuring a 5 page Apple 1 review plus the original first Apple ad.
*2 - On a side note, page 25 features an intriguing ad :))