Learn Russian: Розничная цена значительно выше. - The retail price is significantly higher.

The opposite of розничная (retail) is оптовая (wholesale). So, 'wholesale price' is оптовая цена. This is an important business and shopping pair to know at this level.

Why do we use the short comparative выше instead of более высокая?

When a comparative adjective is the predicate of the sentence (describing what the subject 'is'), Russian strongly prefers the one-word short comparative form, like выше. You would use the two-word form более высокая if it were directly modifying the noun within a phrase, as in более высокая цена (a higher price).

Could I use намного or гораздо instead of значительно here?

Yes, both намного выше and гораздо выше mean 'much higher' and are perfectly correct. Значительно translates to 'significantly' or 'considerably' and sounds slightly more professional, which fits well when discussing economics or business.

Since цена is feminine, why doesn't the comparative выше have a feminine ending?

Simple comparative forms ending in -е, -ее, or -ше (like выше, быстрее, дальше) are invariable. They never change to match the gender, number, or case of the noun.