Family visit visa refusal

[Bamtexltd]

Hi all,
Can anyone help with this refusal please because this ECO upset me with this refusal.
I invite my daddy to visit me and my family in UK for 2 weeks. Below are the document I sent to him
1. Invitation letter & sponsorship letter
2. My partner passport, my daughter passport and my passport pages
3. My payslip & my partner payslip for 6month both almost £2200 per month
4. My house agreement & water bill
5. My bank account statement £2,800 & my credit card statement with limit of £3000
6. My employment letter and my partner employment letter

Father side
1. Employment letter
2. Annul leave letter
3. Bank account almost £331
4. House properties
5. Tax clearance

In my sponsorship letter I mention that I will pay for all the expenses include ticket
And the ECO rang me from Sheffield UK and interview me and he asked me who is going to pay for flight ticket and I confirm it that I will pay for the ticket. Which is satisfied with it according to him that day. But it surprise me when My daddy went to collect his document and it was refused.
Below is refusal letter
I have considered
1. your application and any additional relevant information you have provided with it
2. Your immigration history
3. An interview with your son (sponsor name)

The decision
You are seeking to enter the UK for 2 weeks to visit your son. You have stated that your son is providing accommodation for your visit and I am satisfied he is able to do son
You list the cost of this visit to you personally as £470. As evidence of available funds you have provided bank statement in your name with a balance £331. From the information on your application form and the documents you have submitted, you have not demonstrated that you have funds available for your proposed visit.

But in the form I mention it there that I will be paying for trip but On number 78. of the form which says "the cost of aeroplane" which I mention £470 for the cost of ticket.
Can anyone help me with this please. What can I do with it, I want to reapply and I need a cover letter to back it up. If anyone can help me with covering letter I will be very happy