The very same page puts it at £69k in "labour cost". Which is a bit low for any kind of house in York, but certainly not for a small but well built row house in Burnley. A well built row house in Burnley which will have running water, electricity, glass in the windows and central heating.

The figure also appears to confirm your point about the indicative "labourer" wage - doubtless a semi-skilled person not indebted by any obligations to a manorial landlord - being middle class in relative terms.