Hello Everyone!
My pup Atlas and I want to talk about Splinterlands Season-end rewards and how to obtain them via rating and renting and if it makes sense to do so. For those of you that were renting cards yesterday (day before season-end) you already know what I'm going to be bringing up but first, let’s talk about Season-end rewards and how exactly they work. Skip down to Is it worth it? for those of you trying to make that call while reading this.
Seasons
Seasons within Splinterlands is effectively a mechanic put in place for performing well over a set period and to reset user ratings. Generally, seasons are a couple weeks long and the goal is attaining the highest league you can. At the end of each season users are given chests are directly tied to the league system and the reward you obtain is based on the league you are in when the season ends. As ratings are directly tied to the number of people actively playing, it is important for those accounts that are no longer active that have a high rating to slowly drop to make room for active players and make it more fair for newer players to catch up to the competitive leagues.
Now I'm sure most of you know this already but the rewards tied to leagues go up significantly as you advance through the ranks. Speaking of advancing, there are two pieces to it: Card Power and Rating. I've explained the basics of this in my new player teaches new players guide but I'll cover it again briefly here. Rating is strictly based on how many times you win and how difficult your opponent is. Simply put just keep winning, just keep winning, just keep winning, winning, winning... Card power is based on a value assigned to each card you own. You need to hit a requirement of both to advance and for most of us that means renting cards to obtain enough power.
League Requirements
In the bronze league shown below, you can see that both power and rating requirements are relatively low, Bronze 3 in fact having no power requirement, however as you continue moving up the requirements for power specifically increase dramatically.
If you compare the requirements to diamond on the other hand... just wow, look at that power spike. When it comes to power attributes, not all cards are created equally. More specifically, Gold Foils can be worth 100x in some cases. As an example, the below chart shows just how many cards from the Untamed/Dice/Reward set it would take to get you to each rank.
Quite astonishing when you think about it taking 50k common plain cards to get you there. If each card was .50 that would be $25,000. Now obviously it doesn't make sense to use only common plains to get you there and you should absolutely be using foils instead. For specific card power I keep 
image owned by elclements
Is it worth it?
Like the answer to all the great questions in the world, it depends. In my opinion, it is not worth renting cards solely to boost your league in the lower leagues(Bronze-Gold) for the EoS reward. That said, if you are going to stay in that league for a period it CAN be worth it as the number of chests from your daily quests also increase when changing leagues and not just division. I'll get into the details shortly but in general, the number of chests you receive from going up one rank largely do not contain enough rewards to be worth the cost of renting enough cards to boost you up. This isn't true in all cases as you can sometimes get lucky and snipe a good rental deal on PeakMonsters or you might happen to own cards which put you close to the border but for most of you new players you will end up with less DEC than you started.
So how do we know this and how do we make the decision. Well first of all, it is possible to calculate the average value of a chest. To do so, take the drop % of all possible chest contents and multiply them by the DEC value of the reward and average it out. Even better, hop over to Splintercards, where 
image sourced from https://splintercards.com/tool-lootchest.html
So now that you know what the average chest is worth, how do you know it is worth it? Well, use that average chest value number to calculate the average value of any given league season reward. Surprise, Surprise, Splintercards has that automatically done for you as well.
Now you can really figure out just how much on average you can expect to earn by jumping up to the next league and compare it to the rental cost it will take you to get there.
The Great Card Shortage of EoS
Although I am also new it was easy to tell that it has been a trend for many people to wait until the last day or two and try and rent/grind as high as possible. Unfortunately, this also means that demand for rentals is low during most of the season and then skyrockets at the end pushing prices to crazy high levels. This translates to the cost of renting 10k power easily over 1k DEC. Now you guys can do the math there but at 1k DEC alone is a loss until around Gold II to Gold I and that is even assuming that 1k DEC purchased all the power you needed. In the most recent season end countless people were flooding the game's discord begging for delegations and complaining about rental prices. Unfortunately, I hadn't written this yet to tell them all to save their DEC and that discord flies by so not many could take advice there anyways. Eventually, everyone will learn how this works though and they will opt just not to rent. In a free market, card owners would then drop prices until things are reasonable again. Then again, crypto is a roller coaster, why would we expect Splinterlands to be anything different.
Best of luck out there!
All images and content owned by me unless otherwise mentioned