Staying for more than 90 days would be breaking the law, unfortunately for you. Moreover, the 90-day rule applies to all of the Schengen area, and the Schengen Agreement is now part of EU law. Therefore, by overstaying you would be breaking law of the entire EU, and also the non-EU Schengen members.
The actual penalty for overstaying depends heavily on the circumstances, but there are generally three kinds of penalties that would apply, from most likely to least likely:
A fine. No long-term consequences, but would probably offset your 200$ savings.
Deportation from Sweden. Could be together with the fine. Chapter 8, Article 1 of the Swedish Law on Foreign Nationals (in Swedish) allows deportation in case something is wrong with paperwork or permits, including violations of the Schengen agreement. Section 4 of that Article also allows the same if you do not provide requested information about your stay or lie about it. That is, if you claim you'd be returning within 90 days but show a ticket 91 day later, that's also a violation. Such a deportation may or may not include a reentry ban of up to five years. A reentry ban would be reported to the Schengen Information System, see next point.
An entry ban in Schengen. In this case, you'd have that negative mark on your record in the Schengen information system - important to note that all Schengen countries share this. Article 24 of the SIS II Regulation is what allows a SIS alert banning you from entering based on the decision of an individual country (Sweden in this case).
The consequences may include a requirement for you to obtain a visa prior to future visits, with you no longer being allowed visa-free 90 day travel. The previous sentence is not correct, there's no such provision in the SIS, the entry could merely require that you be denied entry. If you get a SIS alert entry, or suspect you did, it's possible to request to see your SIS entry, and you could appeal the decision if you have an entry ban. A severe option, and extremely unlikely for a one-day overstay.
Now, of course, another possibility is that you do not get caught or get let off with a verbal warning. Sometimes the border guards may not care to even check the dates when you're leaving. Or they may decide to let it slide, but you never know.
Another possibility, though unlikely, would be that border guards not only ask you about your plans on entry (likely enough in itself) but also ask to see a return ticket. Then you could run into trouble already on entry due to your ticket being on day 91.
Now for a couple of practical tips. Sweden does have long-term tourist visas, but they are not an option for you if you're traveling in less than a month - the process takes much longer. Sweden's an expensive country. 200$ isn't much compared to what you will spend over the course of 3 months. I hope it's clear from the answer that the potential consequences of being caught outweigh the savings.
However, depending on where you are staying in Sweden (which has very good train connections), it may be worth to investigate flights from other airports. If you are in Stockholm, and especially if you're south of there, it's easy to get to Copenhagen. If you're in Gothenburg, it's possible to get to Oslo in 4 hours for as little as 46$, so it may be worth it to consider flights from nearby countries in your planning.