Error inserting in table: "Missing FROM-clause entry for table..."

Question

I have three tables:

CREATE TABLE Bebidas(
id SERIAL primary key,
nome varchar(40) NOT NULL,
preco_bebidas decimal(5,2) check (preco_bebidas > 0.00),
    qntd int);

CREATE TABLE Shots(
    id SERIAL primary key,
    nome varchar(40) NOT NULL,
    preco_shots decimal(5,2) CHECK (preco_shots > 0.00));

CREATE TABLE Vendas(
    id SERIAL,
    id_bebidas int references Bebidas(id),
    id_shots int references Shots(id),
    qntd int CHECK (qntd >= 0),
    total decimal(5,2),
    data date);

I created a function SELL when Adm sells a drink or shot automatically be inserted into the sales table. However, Postgresql gives the following error:

ERROR: Missing FROM-clause entry for table "preco_bebidas"
LINE 1: ... T INTO sales VALUES(default, variable, null, $3, preco_bebi... (error in price...)

QUERY: INSERT INTO VALUES sales(default, variable, null, $3, prices * $3, now())
CONTEXT: PL/pgsql Function sell(Character,Character Varying,integer) line 11 at SQL statement
********** Error **********

ERROR: Missing FROM-clause entry for table "preco_bebidas"
SQL state: 42P01
Context: PL/pgsql Function vender(Character,Character Varying,integer) line 11 at SQL statement

The function is as follows:

CREATE OR REPLACE FUNCTION vender(char, varchar(40), int) RETURNS VOID AS $$

DECLARE
    variavel INTEGER;

BEGIN

    IF $1 = 'B' THEN
        SELECT INTO variavel id from Bebidas
        where nome like $2;
        INSERT INTO vendas VALUES(default, variavel, null, $3, Bebidas.preco_bebidas * $3, now());

    END IF;
    IF $1 = 'S' THEN
        SELECT INTO variavel id from Shots
        where nome like $2;
        INSERT INTO vendas VALUES(default, null, variavel, $3, Shots.preco_shots * $3, now());

    END IF;

END;
$$
LANGUAGE 'plpgsql';

The problem is not in ALIAS (AS), already tried and not solved. Help me, I’ve been trying for hours and I can’t fix it.