VueJS unexpectedly runs a function - vue.js

Question

Hello guys specially VueJS devs theres something weird happened. Ill explain it one by one
Full video:
https://drive.google.com/file/d/1G2ksQsMQ1LB868dg29f8mm4NR_x5GycF/view?fbclid=IwAR1YmYbo3J6jHrY6PHd8E_lxA47VJSXV6G3132_uF6Or3bXv7MbnQbRvKaU
I use datatable and then i use this getDefaultPrice() to manipulate the price because the format of my price is like this ("65;75") to return the first value to PHP 65.00
then once i click the add to cart button please see image for codes the getDefaultPrice() also executed.
and I received an error "price.split is not a function" I tried to console.log the function and it really runs it without calling it in my add_to_cart();
<td>
<p>{{getDefaultPrice(product.price)}}</p>
</td>
<td>
<button
class="btn main_bg_color add_to_cart_btn" data-toggle="modal" data-target="#productModal"
#click="add_to_cart(product)"
>
<i class="fa fa-shopping-cart"></i> Add to cart
</button>
</td>
add_to_cart(product) {
this.modal_data = [];
this.modal_data.push(product)
this.modal_data[0].variation = this.modal_data[0].variation.split(';');
this.modal_data[0].price = this.modal_data[0].price.split(';');
this.modal_data[0].drinks_price = this.modal_data[0].drinks_price.split(';');
this.modal_data[0].drinks = this.modal_data[0].drinks.split(';');
},
getDefaultPrice(price) {
console.log("test")
var price_arr = price.split(";");
var default_price = parseFloat(price_arr[0]);
return "PHP " + default_price.toFixed(2);
},