I can't tell you what to do but I will tell you what I did and why.
I purchased additional service years when I retired. From what you have posted, I paid about 10% more per $1000 than you did, but all of it is covered by a capped COLA adjustment. So, if inflation remains low, I am made whole. If inflation goes into run-away levels, I will lose some ground.
Why did I buy the extra pension dollars? Several reasons.
1. I wanted to have three sources of retirement funds with each contributing about 1/3 to my retirement income - pension, Social Security and personal investments. I should be able to live OK on two of the three sources, though trips to Paris for a weekend lunch will probably be out.
My pension was at about the 22% level, while my personal investments were significantly above 40%. So, I lowered my personal investments contribution by a few % points, but raised my pension percentage to about 28%. Social Security will be pretty close to 32%. As you can see my personal money is still the biggest chunk of my income.
2. I wanted long term care insurance, but the current plans are expensive and there is nothing that keeps the insurers from pricing me out of the market as I get closer to an age when I may need it. So, I view my extra pension money, along with extra SS money from starting SS at 70, as my form of long term care insurance. Both are COLA'd to some extent. Not perfect, but less risky, IMHO, than buying an insurance policy in today's market. And, if I never need the money for LTC, I can spend it!
3. My state's pension plans, while not 100% funded are still in very good shape and the current trend seems to be to fully fund current obligations. The state has also made several reforms in pension rules that minimize things like spiking pensions and other misuses. They are also working to control a few of the 'golden handshake' pensions left over from 30+ years ago. This is not an Illinois type of situation.
4. Having two sources of steady income gives me the liberty to invest a little more aggressively and even to spend a little more in my earlier retirement years while I am still healthy enough to enjoy travel, wine, women and song.
All this was done before the pension ruling in the Detroit bankruptcy case.
Since my plan still leaves me with my personal investments providing the biggest chunk of my retirement income by far, I would probably do the same thing again. However, given the Detroit ruling, I would not be tempted today to bring my percentage income from personal investments any lower so as to boost my pension.