expect to pay somewhere around 20E / day for guide , and 50E / day for each vehicle.
When we were in the area ( last month ) we checked with the chief of the Gendarme in InSaleh , he assured us that there is only a requirement for a guide south of InSaleh. The 'border to border' guide requirement is not enforced - we traveled north from InSaleh by ourselves on 2 bikes with the only requirement that we checked in with police & gendarmes and rode north to Laghoat with an organised convoy.
I imagine you might need to arrange for a guide to meet you at the border in case the authorities there are picky ( we had to at InGuezzam, and had to wait for 2 days....), but once inside it's a lot easier.
The older I get, the better I was...