i have the 1.5mill advanced scanner and the detailed surface scanner on a cobra kitted out for exploring. as it stands you will have to sell a massive amount of cartographic data to recoup the 1.5mill (getting anything from 200 creds for a single star system to 12000 creds for a system with 55 bodies in it)
as for the detailed surface scanner , it would be much more enjoyable if the time took to 'discover' the contents was much much quicker, its a very slow and tedious process right now.
have explored something like 770 systems so far and gained 750k in creds so it does add up over time....
You must be doing something wrong. 770 systems should pay out on average (770 x 6500) 5.005.000 creds.