We have 3 sets for DD but one set came with the cot set I have for her.

I got some 250 thread count cotton ones that had some pretty lace stuff on it for $25 at Target. We have a Boori (large) size cot as well so like any bed I did expect to pay more than the smaller sized cots. I didn't see $25 as a whopping expense for a flat,fitted sheet an dpillow case consideringshe will be in the cot/toddler bed for a couple of years.

We change the sheets on her bed once a week (though fortnightly atm coz I cannot be bothered). Unless she floods a nappy or something.

If you are clever enough to make them then do so