Another factor to consider is that the instructor wage has no guarantee's.
For example;
If you need to have at least £1000 coming in each month then instructing means you'll need to have a fallback plan unless you like living on the edge. If you have family then living on the edge isn't an option so it's not uncommon for instructors to have a side line business to contribute to their earnings.
If you are using instructing as a stepping stone towards the airlines then this changes your overall view on the project but bills still need to be paid and loan repayments will get bigger. Just make sure you do your best to evaluate whether you can afford the training and lost income - which means adding anything from 50% to your initial budget as a safety net.
If money is no object then go for it because the GA world needs more dedicated instructors who are in it purely for the love!
VFE.