I also did Shared Risk and got pregnant on the 2nd round (one fresh cycle and one FET), so I technically "lost" about $5000-$6000. I still have no regrets. My first cycle resulted in a miscarriage, and I found it soooo much easier to handle the miscarriage and subsequent round knowing that it was costing me more money -- the money was already spent. And knowing that I could back out at any time and get all of my money back was a relief. I doubt I would have done 6 rounds, but knowing I'd then have some money left over to pursue adoption made a big difference.
And as someone above said, if they accept you into Shared Risk, it's because you're a good risk for them and likely to get pregnant.
Also, FWIW, spending that much in a lump sum put me over the threshhold (7% of income, I think) to be able to tax deduct my medical expenses that year, so I got a healthy refund. If I'd paid for the cycles separately they would have been in different tax years I wouldn't have hit the threshold for expenses.