Maybe the lady feels you are becoming too close or attached to her, and gave you that price hoping it would shock you back to the reality of the situation. Or the agreement you proposed could be outside her comfort zone for some reasons, so she gave you an unacceptably high price.
Agreed.
And before jumping on how the SP in question was out of line for suggesting a very high price, maybe we need more details.
For example, how well does she know the OP? I would not enter into such a relationship with someone unless I already knew and trusted them very, very well.
Consider what she may be giving up - independence, freedom, her already established clientele base. 5k a month may seem like an offer an SP should not refuse, but it really depends on her relationship with the OP, and also what she may have going on in her personal life. Also, what is expected of her for that 5k a month?
I have also been asked for similar arrangements, but I have never taken someone up on their offer because I was not willing to give up my independence and freedom, and I was simply not comfortable being dependent on one person. I guess for the same reasons I would find it hard to be a stay-at-home wife!!
With the right person, I would consider the offer, but there would have to be a lot of trust and affection already established for this kind of thing to work.
xox Charley