In theory you could choose a building firm you own that charges 500k instead of a different one that charges 400k (and even subcontract it to the 400k firm).
If you sell for 1M that means you keep the extra 100k from the building firm and 100k from the land.
If you go with the cheaper builder you only get 120k
If you sell for 1M that means you keep the extra 100k from the building firm and 100k from the land.
If you go with the cheaper builder you only get 120k