I'm still pretty new to selling cakes so I'm having trouble figuring out reasonable prices. A website showed that 3.50 a serving is a reasonable price but that would mean I would sell the cake for at least 280. My biggest fear is telling someone the price and they're going to assume I'm overcharging them so I just need help figuring out if thats a reasonable price for a 2 tiered cake to feed at least 80 people. Any help would be appreciated

There is sooooooo much that goes into pricing:(  There have been many, many posts on here and other sites regarding that topic --  you really need to study those.  Do a google search 'pricing cakes ' and you will find some charts showing the many factors one must take into consideration along with the many reasons you NEED to charge a certain amount.

It has cost you many, many $$ to be able to make a custom baked and decorated cake - YOU should be paid a fair price for it!   ....  YES, indeed a two tiered cake SHOULD sell for that much!!   It takes you time and $$ to produce it. You spent time & $$$ getting the lessons and equipmnet to make them.   Do you ever go into a resturant and tell them how much you want to pay for a steak dinner?!?  OR for that matter, tell the grocery store how much you will spend for the ingredients to make that super nice custom cake?

We all have had to get over the sticker shock to sell cakes.  You don't want to end up paying your customer(?) to buy a cake from you.  That's what you would be doing if you under charge.

Just a couple of reads for you to start your l o n g study of how to price your custom creations: 

http://www.cakeboss.com/Cake-Stuff/how-much-should-i-charge-for-my-cakes             https://www.thumbtack.com/p/cake-making-cost            https://mcgreevycakes.com/how-to-price-your-cakes-shhh-i-didnt-say-that-out-loud/

Look on YouTube.......there are several videos ther that could help you also.