The following tentative calculations are based on Armstrong’s statement of his expenses for the Northumberland map, and estimated print runs from subscription lists for Lincolnshire and Leicestershire. A highly speculative calculation is also presented for Nottinghamshire.

__Northumberland __

In his letter to the Royal Society of Arts in 1769 (Harley 1964) Armstrong estimated the costs of the Northumberland map at £516 10s for a print run of 500 copies of the 9 sheet map. That equates to a cost per map of £1 0s 8d. The proposal price ‘in sheets’ was 1^{1}/_{2} Guineas (£1 11s 6d) indicating that sales of 328 maps would have covered the expenses. We can reasonably assume that the size of the print run indicates that there were more subscriptions than this, so on the face of it the Northumberland map was a commercial success.

__Lincolnshire __

Lincolnshire is 30% larger in area than Northumberland. If we make the crude assumption that we can pro rata Armstrong’s expenses, then the estimated cost for Lincolnshire was £671 9s. Carroll (1996) records that there were subscriptions from 294 names, for nearly 400 copies of the 8 sheet map. If we assume a print run of 400, this equates to a cost per map of £1 13s 7d. The proposal price ‘in sheets’ was 2 Guineas (£2 2s). It would seem that Armstrong had another success.

__Leicestershire__

Leicestershire is a much smaller county, only 40% the area of Northumberland. Once again if we pro rata Armstong’s expenses we get a cost estimate of £204 15s. Welding (1984) records that there were subscriptions from 264 names for 275 copies of the 4 sheet map. If we assume a print run of 300, this equates to a cost per map of 13s 8d. The proposal price ‘in sheets’ was 1 Guinea (£1 1s) indicating that Prior’s enterprise was rewarded with commercial success.

__Nottinghamshire__

Similar calculations for Nottinghamshire are highly speculative because we do not know the number of subscribers for Chapman’s map.

Based on the Essex map we can estimate a print run of 200 maps and a cost of £211 7s giving a cost per map of £1 1s. Unfortunately the proposal price is not recorded, but if, like Leicestershire and Staffordshire, it was priced at 1 Guinea, then Chapman broke even.

An alternative approach would be to use the Leicestershire subscription list to make an educated guess for the print run. Although the names of the Nobility and Gentry are not recorded on Prior’s map, the subscription list is conveniently ordered by rank (Welding 1984 p.51-53). The Nobility, Honourables, Knights and Esquires, account for 49% of the 264 names. There are 58 names of equivalent rank recorded on Chapman’s map from which we might derive a subscription list of 118 and a smaller print run of 150.

Based on the estimated cost of £211 7s, the cost per map would be £1 8s and at a selling price of 1 Guinea, Chapman would have made a loss. However if there were 264 subscribers for the plainer Leicestershire map, it seems unlikely that there were only 150 or 200 for the more detailed, better executed and more decorative Nottinghamshire map.