Ouch, an expensive and unfortunate lesson mlbUMP. I guess the lessons learned from this are:

When violating airline tariffs,

- pay for your tickets with cash or the equivalent so the airline has no means of collecting additional revenue

- book your tickets on different airlines

- don't violate the rules of your primary carrier (that way you won't lose status or a pile of miles)

- try to avoid these practices in the first place (use discount carriers, creative legal routings through cities like LAS, etc.)

- purchase tickets directly from the airline so your travel agency doesn't get hit with debit memos