Was classical BASIC ever used for commercial software development, and if so, how were limitations overcome?

Question

Many of us, including me, started their programming life with programs written on home computers, something like

10 PRINT "ENTER RADIUS"
20 INPUT R
30 PRINT "CIRCUMFERENCE="; 2 * R * PI
40 PRINT "AGAIN?"
50 INPUT A$
60 IF A$="Y" THEN GOTO 10
70 END

Of course, the line-number based BASIC was prone for creating spagetti code, also because most BASIC dialects missed structural statements like WHILE, doing everything but the FOR-loop with IF, GOTO and GOSUB. I'm talking about BASIC dialects before 1991, when QBASIC and Visual Basic appeared.

While BASIC dialects may have promoted bad style amongst aspiring programmers, were there larger commercial projects created in such a BASIC dialect? If so, how did they manage to live with and workaround the obvious shortcomings?

By "serious", I mean:

• Not a game (I know some commercial games were written in BASIC, for example, Pimania)
• Not freeware
• Not trivial, that is, reasonably large (say: at least 1500 LOC)
• Sold to several customers (not an in-house development)
• "Mission critical" is a plus