What sort of budget should one have for the types of trips descibed above.
It is not a matter of "If you have to ask you cannot afford it" but a matter of do I want to go there sufficiently enough to pay what ever it costs.
Been going for 20 years now and prices have changed dramatically but contact a specialist agent such as Go2africa or Rhinoafrica. They will work with you and get a great deal that suits your wallet. Massive, reliable experience of everything out there. They really help and we have used both to great effect in the past. Minimum wage in SA is increasing soon to nearly £1 per hour so deals are always available.....
In the early days, we flew eveywhere internally, including light aircraft transfers into Sabi Sand and Ngala but now those prices have shot up. Return JNB to Kruger MPQ will skin you £250 each for 40 min flights as SAA Express have a monopoly. It was 1/3 of that not so long ago. Skukuza and Eastgate, even more. High end lodges can easily cost £1K per night per person in 2019 (or more) but their drives can go off road, unlike in Kruger itself with self drive.
As others have said, try Sanparks lodges in Kruger. We had a riverside chalet with Brai etc for around £100 per night. Fuel is cheap at around 80p per litre. Sanparks own game drives are ex vfm at under £20 per 3 hour drive. Food is fabulous and cheap. Wine is ridiculously cheap compared to UK. Great wine in a restaurant is usually around £7-10 per bottle. Stunning fillet steak, £10 or so.
Flights from UK. We always go first, business or premium as it's an 11 hour flight and Mrs C is not in best of health. Join one of the fare watch alert sites. We got 2 returns on Virgin Premium for £650 each. Shortly after we booked, economy was double that! Dialaflight got us BA business tickets for around £1500 each last time. Air France is great but 2 hour min at Paris changing flights. Various African airlines offer silly cheap but stop over flights.
Accomodation. Also look at the portfolio website. They have been highly recommended for years, offering B&B for peanuts. SA B&B is in a whole different league to UK B&B! Seriosusly high end establishments for unbelievable prices.
We 'only' spent around £6-7k all in this time, inc premium direct flights from LHR, for 2 weeks there but I reckon you could do it for half that or less if needed. Our first trips cost....well, don't go there! Lottery money.