If your American Express credit card's offer is targeted for the IHG's hotel chain stay, you might be able to score some IHG points at a cheaper rate than the usual 100% bonus points purchase.

My American Express card has a targeted offer for Crowne Plaza and the offer is expiring on November 30, 2018.
  • Spend $250 or more, get $50 back - Crowne Plaza Hotels
I don't have upcoming stays at Crowne Plaza, but the trick is to do a points and cash booking, and that somehow appears to trigger the bonus offer. Let's take a look:
  • Make sure your card is enrolled in the offer. 
  • Go to ihg.com/crowneplaza or whichever IHG's chain hotel site your offer is. 
    • (Optional) Activate your favorite shopping portal's cash back bonuses if any. I am not sure if that will earn the cash back or not on the cash portion since this is considered points booking, but I did it anyway. 
  • Search for the Crowne Plaza Paris - Republique in Paris, France because this Crowne Plaza appears to provide better cash portion to purchase IHG points (Thanks to IHG's current 15% off cash + points booking promotion). 
    • 15,000 IHG Points + $75.65. This represents purchasing IHG points about 0.5 cents a piece. 
    • 20,000 IHG Points + $97.75. This represents purchasing IHG points about 0.48 cents a piece. 
  • Book 1 night and 2 nights because the offer is spend $250. The total comes to $271.15. 

A few minutes after I completed both reservations, I received an email from American Express to congratulate me for completing the task "Great news! You just used your Amex Offer!" The content of the email didn't mention anything about Crowne Plaza. Instead, it states the following:
  • Thank you for using your American Express Card ending in xxxx at IHG PTS & CASH
On the card's activity, it does mention IHG PTS & CASH as transaction, not Crowne Plaza. So for whatever reasons, this triggers the Amex offer's fulfillment for Crowne Plaza. 

In the end, once I cancel those reservations, I'll receive 55,000 points back instead of the cash. This is like purchasing 55,000 IHG points for only $221.15 ($271.15-$50). This presents buying IHG points about 4 cents a piece which is a good deal and below my valuation of IHG points. I know some people get 5,000 Amex Membership Rewards instead of the $50, which is even better if you value Amex points like I do.