Funny that I was also going to post something similar... But after paying close attention to the situation, I thought about what was happening and came to this conclusion.
There are several factors that contribute to this happening:
I noticed that the bots on this site (GG Deals) always search for the lowest price, however, there are websites like Kinguin, Gameseal, Gamivo, G2A, Driffle, etc., that have adopted this "discounted Game Pass" trend, I noticed the "advantages" of buying cheaper, and I saw that the bots are incorrectly retrieving these prices, calculating the final price with these subscriptions, This is what causes some prices to stay at a historical low in GG Deals, but in that case, "false historical low", and even in the statistics on the website. In addition to that, for example, there's the Gamivo website, which has the Service fee + tax, the final price will never be like what we see on GG Deals, and in some cases, even with discount code.
What I strongly recommend is to carefully check each website to find the best final price, and not immediately go for the one that supposedly has the lowest price, because I've noticed that some of them are misleading, and that's how I learned from them.
