Just a few things, all of these prices are for the Xbox market. I got most of this information from internet searches and old YouTube videos. I took all the prices I could find and averaged them below. These aren't 100% accurate but they're the closest I could find. The market is very fluid during TOTY so expect a wide range of prices at first. Remember that this year's market is drastically different from last year's so expect prices to be much higher this time around. To prepare FIFA 15 coins for the coming TOTY.
*These prices are about a day after their card's initial release
I don't have an exact date for when the prices stopped dropping but from what I've seen, only a week or two after the last day of TOTY prices began to settle. Like I mentioned before, I predict that the cards this year will be much more expensive than lasts. It appears that high-rated IF cards this year are way more expensive than they were last. For example, 2014 Ronaldo FIF went for around 2.65m, this year his FIF is 5.3m(up from 2m and 3.3m). Also, expect Neuer to be quite expensive relative to the other defenders. Last year Neuer was rated 86 last and costs around 50k. This year he's a 90 and costs over 200k. You can imaging what a blue 96 Neuer would go for. Lastly, one more interesting thing to watch out for, if Lahm's TOTY card ends up being a RB then expect a higher price than normal for that as well. I think he'll get his at CDM but that's something to keep an eye on.
So if you're planning of picking up a blue card for your squad you're better off waiting a week or so after TOTY. Similar to TOTW, prices will be extremely high right after the cards are released. Meaning if you're fortunate enough to pull a TOTY card, SELL ASAP!!! People will be selling these cards for ridiculous amounts and impatient players with a ton of coin will pay the price to have them right away. YouTubers, streamers and people who don't like waiting will want to play with them right away so there will be demand. Eventually everyone who bought them initially will sell them shortly after at lower and lower prices until they settle. So if you can wait out another week for one, you'd be much better off. Just one more note, the 2015 market is much different from the 2014 one so at the very least expect the unexpected.
If anyone has any information they would like to add or noticed any mistakes please let me know and I will change accordingly!