A lot of flight schools are paying for or giving a deeply discounted MEI and sometimes CFII ratings for instructors on staff.
For the prices you're quoting, I would not get either rating. For CFII, if you teach a school that has sims, a lot will let instructors use the sims for free. You can do 80% of the rating yourself by sitting in a frasca and self-study. Then a couple flights with a buddy + checkride and examiners fee... you shouldn't be paying more than $1500 altogether for a CFII add-on if you are currently teaching at a flight school. If you need a II to get hired somewhere, then find somewhere that doesn't totally gouge you for a 172 or archer, go through the PTS yourself, study as much IFR stuff as you can, chair-fly, and show up ready to get it done in only a few hours. Get a school to pay for MEI.