Intel i5 desktop chips don’t have hyper-threading (SMT) and haven’t for the 10 years they’ve been available. Typically the i7 variant of the same CPU has been about £100 more (roughly 50%). The point about only 5% extra die space makes no difference to the consumer, as there is/was quite a high cost premium on desktops for that feature. Now Intel has removed hyper-threading from most of it’s i7 desktop chips, and you get 2 extra cores over the i5 version instead.