All TRTOs provide their services with the intention of making a profit; there are no charities in aviation. Even the in-house training at easyJet and Ryanair is structured and costed to show a financial surplus (i.e. the accountants can say that initial training is not a cost drain on the airline). This is equally true of the school that trained you for PPL, or IR, or ME or whatever. You are buying a product from a profit making organisation. Get over it.
As others have stated, you have to establish whether the product offers you value for money before you shell out your cash. That's not easy to do, and I would have to say that it's impossible to do before you've even started your PPL training - so, as Rob says, don't sign up for any kind of jet training at that end of the deal. Get a contractural option to do the TR after the fATPL has been achieved; that way you can assess the market much closer to the time that you will be entering it.
As for the quality of the training itself, there is no reason to suggest that Astraeus' training is any worse than anyone else's, including Ryanair and easyJet. They have a reputation to guard, and they use airline-style selection procedures to weed out the no-hopers - however you contract to do the training. I would say that, if you decide to go the TR route, Astraeus is as good a place to do it as any.
Is a B737 TR the right thing to do for you? Only you can answer that. Again, others have warned of the traps of being restricted to one part of the overall market through your qualifications - at the very least, you could have wasted your money if the first job offer you get is on A320s! Some recruiters may resent the route you have taken, and reject you on principle. Others may have the opinion that you've taken a wise course and think better of you for it. Who knows which opinion you will encounter?
My opinion, for what it's worth, is that type ratings are an airline's responsibility and a legitimate charge on their balance sheet (though bonds have for many years offset that cost). I don't agree with a system that encourages you to get a speculative type rating at your own cost as an ab-initio, However, I recognise that the opportunity is there and there are many who will take it. Just be careful how you spend your money!
Scroggs