Unfortunately BUF-PHL hasn't been cheap in years...I grew up in the PHL area and still like to fly home to visit my family and I am constantly doing all sorts of crazy things in order to get there affordably. Back in the mid to late 1990s I was able to find $150 RT fares then it went up to around $300 in the early 2000's and now BUF-PHL is over $400 RT If you can get $188 on UA I would take it because at this point anything under $200 is a good deal. Some stategies I have used in the past are...

Fly from from ROC, JHW, ERI or even SYR (SYR has been the best lately and JHW the is no longer cheap) to PHL.

OR fly into an airport that is somewhat near to PHL such as ABE or even MDT...(1.5 to 2 hr drive to PHL)

AS you can see these options are not great so please take the $188!!!

Take care God Bless and Happy Frequent Flying!!!
-Buffaloflyer