Mine (4040)cost £523 inc vat.
i believe a 300gpd is towards £300
basic booster pump £80, good one £300.
I ran my good pump outdoors for 18 months and broke it. I had an electical problem on the cheap one. Leaving electrical stuff on overnight or when i was out working was always a worry.
As mr oakley said, i had pipes blow off a few times.