how much did the following items cost in 1920s or 1930s?

Television didn't exist commercially until after 1948 - which is when the first modern commercial receiver was invented.

Electric organs - were first produced for home use in about 1934, the earlier electric organs were large specialty organs and were made to order for the space - so each would have been priced accordingly.

This website about the Hammond company can give you details including prices: http://thehammondorganstory.com/chapterxv.asp

The first hydrofoil boat was built in 1906:

See this website: http://www.hydrofoil.org/history.html

I don't find any evidence to suggest that they were available commercially before the 1960s - so the price would have been for a made to order, or do it yourself boat - unable to price for you.

Radios went in a variety of prices - in the 20s a crystal set could be purchased or made at home so prices reflected that. I find prices for commercial radios from table top model for $25.95 to standing floor model of $87.50 - buying on time available. (The 1927 Sears Roebuck catalog)

tough ones, hard to find prices much info on the period but retail prices, ughy

the Baird Model A Television, ( or disc tv ) sold for $31.25 in 1928

Radios varied in price, I got $ 65.00 for the Day Fan Jr 6 tube radio Circa 1920-1921

Hydrofoils, NADA, nothing there

Organs NADA as well, much info but no prices of said item ( Lauren Hammond ) Dated Mid 1930's