I can see both sides of the argument. Companies should train their people if they want to employ them. On the other hand, smaller organisations just may not have the "spare" capacity to afford to train people and then have them leave soon after completion. Recently a new FO left our place after (I think) 3 days. Imagine the cost to the employer if he hadn't bought the rating? So, I can see why the likes of Emerald and BAC Express charge for ratings.
I can't really see why easyJet and Ryanair charge for their 737 ratings. I would assume they'd get their return on investment.
This is something to consider. You've finished your IR. 6 months has gone by and no job or any thing. In 6 months' time you'll have to do a renewal. You are now considering doing an Instructor rating. So, you'll be spending a reasonable amount of cash for a "maybe". I would weigh up the Shed type rating option at this point.
The Shed time has been very useful to the folk who got laid off after Gill went under.
The Shed and the like are very good aircraft to get good experience on. It's mainly hand flying with very little automation. Besides, flying freight is fun. Freight doesn't complain about the landings.