Most people with osteogenesis are not going to cost the NHS anything like £100k (initial investigations, physio, bone-strengthening drugs). The monetary aspect may well not be as stark as OP suggests
There's rather more to it than that - it's not just a case of being fixed by bisphosphonates and a bit of physio. They strengthen the bones to some extent (not perfectly - it just reduces fractures as I understand it) but all your connective tissues (tendons, ligaments, skin, blood vessels, muscles...) are still affected.
I've had major spinal surgery (told the cost of that was £50k, 15 years ago), various A&E attendances for fractures (inc one emergency surgery), surgical tooth extraction due to teeth not forming properly... and there was another major op that could have been caused by OI too.
Two affected family members have had early, severe hearing loss and so needed audiology care from early adulthood onwards (I may yet go the same way). It's not just hearing aids - there's been surgery, MRI scans etc. One needed a heart valve replacement (and when that failed, he died). Surgery for torn tendons.
£100k is probably a conservative estimate of how much I've cost the NHS so far - and I'm probably only 1/3 of my way through life.
Sorry to be this blunt, but what would be the rules if you decided to terminate the pregnancy should the fetus be determined to have the condition? Would they fund another cycle?
The whole point of PGD is that so that only healthy embryos are implanted, so that wouldn't be the issue. If, however, I conceived naturally I'm not sure if type 1 can be diagnosed in utero as they tend not to fracture in the womb (unlike more severe types). If I gave birth to an unaffected baby naturally they'd never fund PGD at all.
I'd terminate if it was type 2 (will die at birth anyway) or type 3 (very severely disabled) but while I'm very pro choice I'd have to think carefully about having a termination for type 1 (my type) if the wanted pregnancy was significantly far along. I don't believe that my quality of life is anywhere near poor enough to count as 'not worth living' so I'd struggle with the idea that the termination was in the interests of the fetus. I don't want to turn this into an abortion argument, but I just don't know what I'd do in that situation.