Valentine's day falls on February 14th every year. It originated to honor Saint Valentine, a Christian martyr. There are a lot of different stories about Saint Valentine such as he restored a vision of a blind girl, wrote a letter signed with "Your Valentine" before the execution, and even performed a wedding for a Christian soldier who was forbidden to marry. The day became associated with romantic love in the 14th century and grew into an occasion where couples express their love by sending gifts and cards. Although it is celebrated by people around the world Valentine's day is not considered a public holiday in any country.
No, you don't have to. You can, of course, send presents such as flowers and other gifts if you can afford them but it is not mandatory. Sending cards is good enough for you to show people you care. Instead of spending too much money on presents, you can spend more time crafting some beautiful poetry for your cards. When you put more effort into the cards, it will be more meaningful for you and the person receiving the cards.
Not everyone buys fancy and expensive cards. Some people just buy regular cards and do not pay too much for them. If there is a number about the number of money people spend on valentine's cards and the number seems big, it's because it is a collective number. Since almost everyone buys valentine's cards, the total number might seem a lot. Of course, the card publisher and company gain a lot of profit out of it but the number spent by each individual is not that much.
There are a lot of ways to get valentine's cards for cheap. First, you can go and get some basic cards from craft stores and decorate them yourself. You can also get well quality cards from dollar stores. The second way you can get them for cheap is by buying them the day after valentine's when everything related to valentine including chocolate and cards is at discount. You can buy the cards now and use them for last year. Lastly, you can of course make your own cards. Make sure that you only use the materials you already own so you do not end up wasting more money on the materials.