I've been doing some research into Sir Walter Manny, one of Edward III's most prominent knights (quite a character!). In 1372 he died, and John of Gaunt paid for 500 masses to be said for his soul, presumably at the Charterhouse Carthusian monastery where he was buried. But how much was that? How much might you expect to pay for masses for the dead? Was there a fixed price? (I realise that the medieval Church's flexible attitude to money would mean that even if there was an official price that's not necessarily what you would pay, but even a rough estimate would help).

When I was at school 50 years ago it was five squid, Anglo-Norman.  Though that doesn't answer your query about how much it cost in medieval times, sorry.

Found this, does it help?

From: "Saving the Souls of Medieval London: Perpetual Chantries at St Paul's Cathedral, c.1200-1548." by Dr Marie-Hélène Rousseau, Ashgate Publishing Ltd, 2013
ISBN 1409482073, 9781409482079

Google Books : Saving the Souls of Medieval London

"Provisions for John of Gaunt’s chantry reveal in detail the solemn aspects of the obit and its financial burden. As part of their obligations, the Dean and Chapter were to pay the cost of the anniversaries of the duke and duchess, held on 4 February and 12 September, respectively. At both anniversaries, a placebo and a dirige, with nine antiphons, nine psalms and nine lessons, and on the following day, a mass of Requiem at the high alter were to be celebrated with music. All cathedral members were required to attend and to take part in these celebrations. In return they received a stipend, varying according to their status in the cathedral hierarchy. City officials were also paid for attending these two anniversaries. A surviving list of disbursements for the anniversaries of the duke and his consort indicates that the costs of these various charges amounted to £12 per annum. One hundred and eleven obits celebrated annually at the cathedral at the beginning of the fourteenth century generated an income of £183 18s 3½d. These celebrations of obits brought more than financial rewards to cathedral members; the impact of these ceremonies on the overall liturgical life of the cathedral should not be underestimated."

So £12 per annum would buy you a very lavish two-day celebration in a major cathedral, with full chapter and choir etc. (for the time £12 is a hefty sum, but then John of Gaunt had been probably the richest man in England). But how much then for a simple anniversary requiem mass by a solitary priest in a chantry chapel, or a small parish church?

Dr Rousseau's text continues (see the Google Books link above):

".... For example Fulk Lovel's foundation allocated 100s annually for the chaplain's wages and 50s for the anniversary. In 1314, similarly, Richard Grene/de Gravesend allocated 100s to the chantry chaplains and 40s for his obit. ..."

So as I take it one had to provide a contribution (say 100s per annum) towards the annual wage of a chantry priest (who was presumably getting payment from the estates of many other deceased as well), but in addition had to provide a not inconsiderable sum (perhaps 50s, ie about half the chaplain's annual wage contribution) just for the anniversary 2-day celebration of the requiem mass (the obit).

It was money for old rope really so no wonder Thomas Cromwell put a stop to it all in 1538. But ever mindful of Priscilla's 'Benefits of Religion' thread, I do duly note Dr Rouseau's comment: "These celebrations of obits brought more than financial rewards to cathedral members; the impact of these ceremonies on the overall liturgical life of the cathedral should not be underestimated."

Interesting, very interesting. So John could potentially have been laying out well over £1000 (hundreds of thousands by today's standards). Generous indeed!
£5 in 1965 would have been around 3s in 1372, so prices have dropped...
Thanks, LadyinRetirement and Meles meles.

Thinking of Thomas Cromwell, Manny's tomb was destroyed thanks to the Dissolution of Monasteries. It was rediscovered in 1947 but I can't find out if he was reburied in the same spot (now a garden) or moved elsewhere. I contacted the Charterhouse so hopefully they might know.