Prices

price is cast with money-for-laravel’s AsMoney::currencyColumn('currency') to a RoundlyConsulting\Money\Money: the amount lives in price as minor units (a decimal(38,0) column), the code in currency.

use RoundlyConsulting\Money\Money;

$ad->price = Money::ofMajor('15.00', 'EUR');
$ad->price->minor();        // "1500" — a string, never (int)-cast it
$ad->price->toDecimal();    // "15.00"
$ad->price->format('sk');   // formatted for the Slovak locale
$ad->currency;              // "EUR"

$ad->price?->add(Money::ofMinor(500, 'EUR'));      // money's API; mismatched currencies throw CurrencyMismatch

Advertisement::query()->orderBy('price')->get();   // numeric order

Rules

• Only Money|null can be assigned; anything else throws RoundlyConsulting\Money\Exceptions\InvalidMoneyValue.
• Assigning a price in another currency to a priced ad throws CurrencyMismatch — set currency first to re-denominate on purpose (UpdateAdvertisement does this for you).
• Writing null clears the amount and keeps currency.
• PostgreSQL and MySQL store all 38 digits; SQLite is exact only within int64, so the cast refuses wider amounts there (InvalidMoneyValue) instead of silently storing a float.
• The text-ad fallback renders $ad->price->format() in the active locale.

API resources

Render the price with money’s resource — from() returns null for a price-less ad:

use RoundlyConsulting\Money\Http\Resources\MoneyResource;

'price' => MoneyResource::from($ad->price),
// {"minor":"1999","decimal":"19.99","currency":"EUR","exponent":2,"formatted":"…"}
// "formatted" follows the active app locale: app()->setLocale('sk') changes it

minor is a JSON string on purpose; a frontend doing arithmetic reads decimal (or BigInt(minor)). formatted follows the active app locale (app()->setLocale()), so it changes with the request’s language — display it, never parse it. Arithmetic, formatting, currencies and rounding are covered in the Money for Laravel docs.