Suppose the mortgage is 500, and rent 600. 100 profit for the landlord.
If tomorrow the mortgage increases by 200, the rent will have to increase by the same amount to maintain a profit margin of 100.
If you're asking why was the rent "only" 600 and not 800 in the first place, is that your price is affected by demand and supply. If your prices are ridiculous, nobody'll rent from you. But if everyone around is on a Buy to Let scheme and mortgages (thus rents) rise, your tenants will have to accept your rent increase because all supply has become more expensive. No one is leaving money on the table. It's markets 101.
Suppose the mortgage is 500, and rent 600. 100 profit for the landlord.
If tomorrow the mortgage increases by 200, the rent will have to increase by the same amount to maintain a profit margin of 100.
If you're asking why was the rent "only" 600 and not 800 in the first place, is that your price is affected by demand and supply. If your prices are ridiculous, nobody'll rent from you. But if everyone around is on a Buy to Let scheme and mortgages (thus rents) rise, your tenants will have to accept your rent increase because all supply has become more expensive. No one is leaving money on the table. It's markets 101.