Now, while getting IVF treatment on the NHS is limited to those under 40, presumably even those who go private will still have all of their antenatal care and delivery on the NHS, and the older the mother the more likely that care will need to be more intensive and expensive, so we are still paying for it somewhere.
Where are you statistics regarding the age of the average woman who receives NHS IVF treatment?
You seem to assume they're all 'older', so I'm concluding you mean 35+?
I'd be interested in seeing if the facts back that up.
Where's is the evidence that women who conceive using assisted conception experience more complications than women who fall pregnant naturally.
Maybe we should just stop all these 'older mothers' altogether so 'we' don't have to pay for their selfish desires?

My very point is that nobody NEEDS IVF, because nobody NEEDS to have biological children. Unlike needing life-saving treatment, having biological children is a want, and unlike treating obesity or smoking-related illness, there are no benefits to the taxpayer or the NHS in the form of significant later savings and future good health for satisfying that want. If anything it may create future health problems because we are not yet fully aware of the long-term health implications of IVF.
Using your reasoning, however, nobody NEEDS to smoke or overeat, either. It's elective behaviour to pick up fags or not exercise or eat too much.
Nobody NEEDS to drink alcohol and become violent. It's a real burden on the taxpayer when they wind up in A&E with alcohol-related injuries, shall we just not treat them because their selfish need to get p*ssed is cost-prohibitive?
What about cancer drugs that are not going to cure the patient, but will extend their lives for a few months?
Is it selfish of them, to want to live that much longer and be such a burden on the taxpayer? I mean, these drugs are not curative, they're just prolonging the inevitable. So by your reckoning, since they don't really NEED to live longer, shall we not treat them, too?