Back in good old days, you simply bought the 15" base model for $1800 and then you could max out every single spec by upgrading all the components yourself. And then you had a fully decked out 15" MBP around $2200, while if you maxed out every spec from Apple directly, you paid over $4000+.
That is why Apple killed the right to repair, as Apple wanted us to pay for their super overpriced hardware.
In the end, it worked out very well for Apple.