"Integrated metallic testing on the combo cards helps reduce truck rolls" I can't stress this feature enough. Being mainly a data only CLEC, we wanted to buy the cheaper, non-combo, data only DSL cards. However, Adtran, Calix, Zhone, and Nokia confirmed that without the SIP to FXS combo function, you loose the
Integrated metallic testing" This means you can't test loop length (without a dsl modem trained on the other end), can't test if you have a cross, foreign voltage, etc. Yes, this can be done with a field tester, but the cost of sending a tech out to do that is much more of an expense.
DSL only data ports were around $30 a port, and combo were like $50 a port from what I remember.