How much is mabel attwell tea pots?

I don't have enough info to answer this question exactly. I can tell you whether your teapot should sell well. A Mabel Attwell Tea Pot is a highly collectible item, and judging by the looks it should do very well on the market today as in the past.

This one sold below, it is the Shelley 'Boo Boo' teapot. It is hand painted as I am sure all of these are:



Stock No. 243

A hand painted Shelley "Boo Boo" teapot, formed as a house in the shape of a mushroom, designed by Mabel Lucie Attwell in 1926. This example is the smaller of the 2 sizes produced, is in very good condition with no damages or repairs and only a tiny fleck of orange paint missing from the tip of the spout (see photo above).
The base bears the green printed mark for Shelley "Shelley" and "England" below that mark, also the Registered Design Number "RD.724421" (dating to 1926) printed in black.

Dimensions :
height : 4.25 inches

Sold

This was made in the UK, note the Registered Design number. These were very popular in the UK and this one sold for 220pounds or 351.00USD.




Stock No. 243

A hand painted Shelley "Boo Boo" teapot, formed as a house in the shape of a mushroom, designed by Mabel Lucie Attwell in 1926. This example is the smaller of the 2 sizes produced, is in very good condition with no damages or repairs and only a tiny fleck of orange paint missing from the tip of the spout (see photo above).
The base bears the green printed mark for Shelley "Shelley" and "England" below that mark, also the Registered Design Number "RD.724421" (dating to 1926) printed in black.

Dimensions :
height : 4.25 inches

The Sadler Racing Car design sold on eBay in June 2004 for over 800.USD.

I would say your teapot is somewhere in that price range! Without knowing which one you have, I cannot say for sure, but it should not be thrown away!