Know who you are buying from and know your Cotton.

First of all, cotton in Egypt specially the organic one is priced according to the weight. The higher the TC is, the more cotton it will contain. So the higher the TC, the higher the price would be.

Second, the feel of the Egyptian cotton. If it was 100% cotton and depends on the quality of the cotton, it should be very soft, not ruff and not just smooth. There is big difference between soft and smooth.

Third, 1000 TC, 1200 TC and 1500 TC should not be by any means less than 4kg/8.8lb. The less the TC is, the less the weight is going to be. The more weight it is, the more cotton you got in there, thus the higher TC and quality it is.

Easiest way to know if you got the advertised thread count is to follow this chart.

80TC - 120TC (no less than 1.2g / 2.6lb)
130TC - 180TC (no less than 1.6kg / 3.5lb)
190TC - 300TC (no less than 2kg / 4.4lb)
310TC - 500TC (no less than 2.2kg / 4.8lb)
510TC - 800TC (no less than 2.6kg / 5.7lb)
810TC - 1000TC (no less than 3kg / 6.6lb)
1100TC - 1200TC (no less than 3.2kg / 7lb)
1210TC - 15000TC (no less than 3.8kg / 8.3lb)
(all wights are qouted using king size sets. To get the weight of the queen size sets, minus 0.2kg / 0.4lb)

Since there is no way for the buyer to know what is the actual thread count of the received bedsheet, then you must go by weight. Ask the seller before you buy about the weight. Thread Count is no more the way bedsheets should be sold, to avoid all false advertising.
I do hope that this will help to eliminate the bad sellers that are listing higher TC then their sets really are thus defaming the reputation of Egyptian Cotton.